The single best DPS sword in this case would have to be Acheron, since the OP damage buff to it. In nearly any case other than Undead or Fiend, an acheron is going to have the highest DPS... Even then It's arguably just as good as some other weapons that specialize for those monster types. However, that's kind of boring. If you were looking for other good alternatives, I'd say that there's the obvious FF/BTB option. I prefer FF over BTB because they're identical minus the charge attack, and if you use a FF for a bit and get the charge down just right, It's much more powerful. Other good choices include the DVS (I'd say don't bother with the Wild hunting blade since you have Skolver (Even if you didn't I feel the DVS is better)) and the Gran Faust (for heavy knockback and wide sweeps). If you manage to curse a wolver, it'll do about as much damage to itself as you will.

Not to sound like a huge DVS fanboy, but... yeah. It's my favorite sword to use IF I COULD ONLY HAVE ONE! Firstly, I feel it is the only normal damage sword with viable damage. Levi, CIV, and the Suda / Triglav all are so weak in comparison to weapons that have a specialized field that they're unusable except for utility (knockback charge attacks). Next, the incredible attack speed of it allows for you to capitalize as much as possible in a gap in an enemy's defense. If you're fighting monsters with quick cooldowns between attacks, you can always get in and hit them once or twice before throwing up your shield or dashing away to avoid damage. So in that way it allows for damage with surviablility.
Poison, is always a great status to be inflicting on enemies as it raises your damage and lowers theirs and prevents healing. And the DVS inflicts strong poision, so that will actually be of a noticeable benefit. Also, it's a fairly unique fighting style. There are only 2 versions of it really, the Dread Venom Striker and the Wild Hunting Blade where as the Bandish has 5 variants, and other "Medium" style swords function very similarly like the Leviathan blade and Cold Iron Vanquisher. Similarly, there are many heavy swords that functionally are the same, but with different damage types and statuses. There's really just nothing else like the DVS.
I take the DVS over the WHB because a specialty against beasts means it's going to be slightly weaker against all other enemy types, and it lacks poison. Plus, hopefully your gear provides you with damage Max against all enemy types with any sword which would make the beast high bonus useless. Finially, I find that with the Scorching Barrier Drakon ability (3 larger fireballs), the DVS is one of the most efficient swords to dispatch large enemies. Giant Lichen colonies and Lumbers in particular are a prime target. With fire and poison as well as the damage from the circling fireballs, their health bars generally slide away into non-existance in a few seconds. This can work on Trojans as well in a pinch when you don't have time to charge a Blitz Needle.
So all in all, I find it to be a sword that reliably mixes high damage with survivability and utility (Good for moving through the curse seed in Shadow Lairs) that can be used in all Swordsman situations. A must have for any Swordsman with extra weapon slots.

It can generally be hard to get every hit from the DVS to connect and a lot of people feel this makes the sword a bad option. However, just because on lighter, easily knocked around enemies in an open space some of the attacks won't hit does not mean the sword isn't still one of the best over all options. You said you frequently use it against large enemies like lumbers and dreadnaughts, and that's certainly where it's full potential shines through. Especially with lumbers, you can "dance" around them avoiding all damage and dealing a great deal. The other thing that you'll need to learn to do is to use the many steps and the large ground you cover during a full combo to work an enemy into a corner and then they're toast. You probably know this already, so it's for other people who either already have the sword and over look its potential, or people thinking about getting it. I think you have the right idea with how you're using it, and it sounds like you've found a way to make the Maseraith cloak work with it well :)

I think that's an excellent starting point. You have a good mix of defences, bonuses, and damage types which makes it a versatile loadout all around. I would urge you to upgrade your DTS to a BTS though, for the passiveDamage Medium bonus. However, the Level 1 5* shield will have less... shieldiness than the level 10 4* one, so if you're unable to forge it at all, that is something to keep in mind. But if you feel you can make due with being able to take a few less hits in order to dish out more damage, then that would be a great first step for you.
Advice I would give you though. In this game (as well as most) it's good to specialize heavily in one area instead of trying to widely spread your abilities. Often, you end up simply being mediocre at everything rather than Excellent at a few. The gear you have right now all can be used to specialize in different aspects, and be used very effectively there. Skolver, for example, is the choice armor of Lockdown. Vog, on the other hand is many people's go to choice for Swordsman gear for Firestorm Citadel. I think at some point you should try to round out both sets in order to be more specialized, but for now, the mix you have will allow you to get money from nearly any source, making the end goal easily achievable.
I started out by getting full Vog because I liked the ASI and had a BTS for damage. I used that to grind FSC enough to make a good set of Snarbolax armor because I realized that weapon UVs can provide ASI but only armors will give Universal damage bonuses (rather than a damage bonus to a single monster type). You may want to keep this in mind. ASI is very important for swordsmen if you want to survive through most fights while dispatching of your enemies in a timely maner. You *CAN* win fights by doing 1 or 2 hits then running out of range of the enemy attacks, but this takes a long time (especially on elite). ASI allows you to use a sword's full combo before the enemy can attack you back, in general. That being said, if you have no Damage bonus, it can be difficult to stagger enemies and interrupt their attacks (which is the other form of defense you have). It may be smart then, to complete your Vog set and use that to do Firestorm Citadel runs in order to finish up your Skolver or start some Snarbolax armor. And then if you buy Weapons with ASI, you can passively have incredible Damage and Attack speed increases.
I strayed from the point there a bit didn't I...... Yes, the Acheron will do more damage to beasts than a BTB :D

The Combuster will keep you alive much longer than a FoV ever will. Yes the FoV can get you out of a sticky situation where you're totally surrounded, but other than that particular incident, it basically laughs in the face of survivability. It has fairly awful attack speed, some where between Divine Avenger / Gran Faust and a Brandish / Calibur line. Its standard attacks are also much weaker than any of the elemental Brandish weapons. Lower damage = more living enemies = more zombies Lebron Jamesing across the map at you. Not even to mention the dang self fire.
The Combuster, on the other hand, has many wonderful qualities that can help you survive even the sketchiest of encounters. The natually quick attack speed can allow you to get in and out of an engagement before enemies close in on you or use their long winded attacks (looking at the Zombie hop aka the Lebron James). The naturally high damage can dispatch the baddies quickly enough to get you out of a fight before you make a fatal mistake. After all, if you're always in combat, you will get hit at some point. And finially the charge attack. Like you said, It excels at knocking back narrow groups of enemies to extremely distant points. If you're facing a group, your best bet is to lead with the attack to knock off a huge chunk of the mob's health and to spread them out a bit if you'd rather pick them off one at a time. The fire also will not stop knockback as Shock or Freeze will from the Voltedge and Glacius, which creates an even wider gap between the enemy and you. Putting distance between yourself and your target while at the same time dealing heavy damage to him and his buddies primarily the best way to survive long fights. That's why people like the Leviathan blade (but it lacks the damage) or the Divine Avenger special attack (Which takes a long time to execute and makes you move more slowly). Lastly, the long range of the charge attack can be used to safely deal with otherwise troublesome enemies such as turrets or an annoying silkwing behind a wall of vicious villians.
To deal with the period of vulnerability after you use the Combuster's charge attack, you can try to shield cancel the animation. This is where you use your shield shortly after releasing the charge attack to make your knight put up his shield rather than do the whole attack animation. This allows you to get mobile again more quickly, as once your shield is up and the animation is cut short, you are free to move around again. Using this with a quick dash to the side can put you in a whole new location than the one you were in a mere fraction of a second after using the charge attack. Or, if you prefer to save your dash for another oportunity, you still have your shield up at this point, which should block at least one attack in Teir 3 on Elite.
So all in all the Combuster is a much better sword for surviving during fights. However, if you do find yourself surrounded I would recommend trying to shield bump the enemies away. If there is more than 1 layer of enemies around you though, that won't work, so you'll probably then want to try a shield bash. If your shield's been damaged while trying to shield bump, the bash won't work, so your next best bet is to spam dash to get invincibility frames and swing your sword as much as you can in one direction to try to work your way out. The higher Attack speed of the Combuster will allow you to break out of this kind of situation easily enough. You will probably take a hit or two, but hopefully you won't die (and that kind of is worst case senario).

My honest opinion as a Veteran Swordsman. That guy's a chump. A CHUMP!!!!!!!!!!!!!!!

I personally would go with the Gran faust in that situation. That's just because I feel like the areas Shadow Swords excel in (Jellies, Gremlins, and arguably Beasts) Are all better served with a heavy sword. I find that the knockback and damage of the Gran Faust provides a nearly impenetrable defence against Jellies because of their insanely limited attack range (other than the floor spike attack, which you just have to pay attention for). Because they have to move into melee range to even start telegraphing their attack, with ASI vh from vog, you will have ample time to do a 2 hit combo which will either knock them totally out of the range in which they could hit you, or it will interrupt their attacks entirely.
However, the line blurs a bit with Gremlins. Because of their attack range, mobility, and versatility of attacks, a quicker sword may be better suited to put out plenty of damage while ducking attacks to keep from being plowed into the ground. Both a Gran Faust or Obsidian Edge will stagger them, so if you manage to corner a Gremlin, it's pretty much game over for him with either weapon. However, the large knockback provided by the Gran Faust may make this easier. Granted, under perfect circumstances, the Obsidian Edge may do just as much, if not more, with a full combo, but that can be a bit trickier to pull off in a non 1v1 situation. Obviously the Obsidian Edge has an infinetly superior charge attack that will prevent the healers from being so annoying, and that's another important thing to take into account. All in all for Gremlins, I think the sword you chose would come down to personal preference of Sword fighting style, I've always been partial to a heavy sword with plenty of ASI.
And lastly, beasts. The damage dealt by either a Final Flourish or a Barbarous Thorn Blade are fairly mediocre at best. If you even manage to land every single hit (which is a task all its own) the damage will not be anything spectacular, in fact not even as high as an Acheron. I think that Shadow Swords are an incredibly viable option to take to any beast strata, especially when you consider the tendency of them to feature constructs (rather than having a loadout filled with piercing). Again, I think the final decision will come down to preference of play style. Beasts do like to pop up in large groups behind you all at once though, which is a perfect set up for a wide sweeping Gran Faust to do devastating damage. Side bar, I like to take a Dread Venom Striker with me to Beast Strata, and having an enemy cursed and poisoned at the same time is a sight that gets me giggling like a school boy at a fart joke.

The Acheron is the most powerful sword in the game. It can deal insane damage against 4 out of the 6 monter types right now, so what you're going to need is a weapon to fill the last 2 places that one misses. Namely, Fiends and Undead. You would be wise then to either choose an elemental weapon or perhaps a piercing weapon. Let me say that the piercing weapons do have relatively low damage compared to brandishes though, so if damage is a major factor in your choice, you might want to steer clear.
My first instinct is to recommend a Divine Avenger. I find that I actually prefer to use this against Fiends over a sword specialized for them for a couple of reasons. Firstly, Devilites: they're really small and jump around a lot, so other than the first strike of a Flourish, the other attacks and be very complicated to try to land on one of the little guys. The long reach and wide sweep of the Divine Avenger can create a large enough area of damage that the fiend who just dashed out of the reach of a traditional sword may still be caught in your attack. And as devilites have their standard ranged attack (throwing chairs or cups or fireballs or whatever) interrupted by ANY weapon damage, the wide swing can be used to effectively passify an entire group of the monsters all at once.
Secondly, Greavers. Again, they have their attack interrupted by ANY form of weapon damage. They have the tendancy for some of them to fly straight up to you and for some to kind of circle around behind you before attacking, so the DA is very usefull here because you can swing one direction and hit a 180 degree arc in front of you then spin around with the second swipe to hit the other 180 degrees behind you. This will create a system where you are knocking back and passifying a full 360 radius of greavers around you, keeping their agro and avoiding all damage. Obviously the sword is slow so you may want to try to get ASI medium on it or use a Swiftstrike Buckler, but you should be able to find a way to make due.
And finially, Gorgos. I feel that these are perhaps the most dangerous monsters for Swordsmen as it stands. Close contenders are Scarabs and the mini Jellies in compounds, but persnally I have the most trouble with Gorgos. It seems that the second hit of a DA will nearly always flinch them and thus interrupt whatever it was that they were doing (on elite). That's a great way to keep yourself safe from their annoying bites. Also, with their tendancy to drift around the field during their non attacking moments, a wide and long attack range is perfect to make sure you don't hit air where there was just recently an enemy, and open yourself up to an easy attack. In addition, the charge attack can be used to push them back and deal significant damage from a distance if things really start to turn sour.
And of course the DA works well for Undead. It always has and it always will. You just have to teach yourself how to use the different play style. Between the knockback and the surprising amount of mobility you have while attacking, the Divine Avenger can be one of the most effective defensive weapons. The mobility comes by doing the trick where you start to partially do a charge attack after your first hit and then releasing after 1 step to go into your second hit, if you were wondering.
And of course I think the other good option here would be an elemental Brandish. You may consider a Voltedge or Glacius rather than Combuster because you already have an Acheron for raw damage, so having something with a useful status effect may be a good option for you. Because when you are only going to be using this weapon for 2 monster family types, it may bring you some peace to know that it can actually have other uses, like crowd control.
Final option would be a Dread Venom Striker. Real quickly, again the fighting style offered by this sword is very unique and suited for survivability by "walking" out of a crowd, the Poision offers decent status support, it is a Normal type weapon so you can always depend on it, the damage is actually surprisingly high (not near in the same league as the Acheron, but it does deal Strong Poison which will buff your main weapon), and the speed of it can just be a breath of fresh air from the otherwise standard 3 hit combo of a Brandish. That's just some food for thought...