(Gran) Faust for gremlins and slimes
Dark Briar Barrage for beasts and fiends
Polaris for constructs and undead.

That pretty much covers every damage type and every weapon type :D

The three things I would add/change to your general layout is:

- Get a BTB or FF. It is exceptional against some of the hardest mobs in the game (read: Devilites, Greavers, Alpha Wolvers, Trojans).

- If you get a BTB or FF then I'd recommend getting a shadow sword since with two different damage types on swords you perform better than Leviathan against 4 out of 6 mob types and are on par with Leviathan against the other two.

- Consider getting a BTS. In my experience a BTS can take one hit from most enemies. The only things that generally break it are status aligned Lumbers, Vanaduke's Mace (although no damage goes through for me just status so one remedy and I'm good), and Alpha Wolvers (but really what shield can take an Alpha Wolver?). I've become rather proficient with dodging so I only really need to take one or two hits at a time anyway.

"Divine Avenger, Gran Faust, BTB, Polaris/Blitz Needle"

Another convert to the piercing/elemental/shadow way of thinking. Hooray!

I'd just like to point out that although BTB is more popular than Final Flourish, Final Flourish is just as good.

I'd just like to point out that although GF is more popular than Acheron, Acheron is just as good or arguably better. You could easily go Glacius+Acheron instead of DA+GF. In fact, I used to do DA+GF+BTB, but now I usually do Glacius+Acheron+BTB. In FSC I go DA+Blitz+Shivermist.

Using Valkyrie helm with Dragon scale mail is good. If you wanna do PVP, Crown of the fallen is better than valkyrie.

All four defenses, plus medium feind and beast bonuses (both weak to peircing), plus half posin and half curse ressist. (with fallen, you get ASI low, half curse weakness and full fire ressist for PVP)

So you've got defense for any level, and you can carry a shadow and an elemental since you don't need a peircing as much.

I recommend that you stop selling stuff. Maybe I'm naive about the amount of money that can be made, but I think that you want to get more information about how these swords behave, before you discard them. That is, don't sell them, but don't upgrade them immediately, either. At least half of the cost in making a 5-star item is in upgrading from 4-star to 5-star. So put off upgrading from 4-star to 5-star until you know you want the 5-star version.

Leviathan Blade and Cold Iron Vanquisher have awesome charge attacks, for two reasons. First, if you're stuck in a crowd, you can blast everything around you. But be careful doing this in a party. Second, if the enemies don't get knocked back (e.g. they're stationary), then you can hit three times for huge damage. This is more easily done with CIV than with Levi, because it has lower knockback. Despite all this praise, there is little reason to own either Levi or CIV, if you are going to be carrying at least two swords.

Well, at some point you're going to want to have a shadow shield, and it might as well be Crest of Almire. So that's valuable.

I've never used FoV, but I've read about and observed its behavior. It's slower than a Brandish. In regular attacks, it does less damage than a Combuster. Its charge attack is awesome — basically Leviathan/CIV with lots of fire — but I think you need some serious fire armor/trinkets/UVs to avoid killing yourself with it. I mean, this thing will ignite you. And it's probably not a great choice in FSC. So it seems that it's not a very practical choice for your only elemental sword. But maybe some more knowledgeable people will disagree.

The rest of your progress sounds good. At the risk of being annoying, I must point out that your Snarbolax-farming process could be replaced with simply buying a 2-star Flourish, recipe or premade (because FF is just as good as BTB).