For bombs, both fire and graviton are definitely worth upgrading :
- trinkets ? You didn't talked about that
- fire with shock is a great dps combo for huge crowds
- graviton/electron, coupled with good teamates, can clear things VERY fast. And it's fun too.
- if you often use freeze, venom veiler makes a good combo with shivermist.

As for your swords, some nice additions would be :
- trinket too ?
- Snarbolax armor to have some shadow armor with swords bonus
- DVS, although not that good, is fun to use, it is worth the try. It's good against Vanaduke mask phase (perhaps superior to Leviathan, but i didn't do the maths)
- a shadow shield for those pesky devilities is totally worth it.
- you already have a Divine Avenger. If you like it, by all means do a Gran Faust.
- a Fang of Vog ? Not really useful, but it's fun to roast JK from time to time. And I think it can actually OS Slags in Vana P5 (but not sure about that).

That's about all I can think of, but that's still quite a list.

I've seen Graviton Vortex used very well in FSC. It speeds up all of those crowd-of-zombies fights, by letting one sworder do huge damage to every zombie in the room. I've also seen Voltaic Tempest and Stagger Storm used well. It turns out that there's whole world beyond Shivermist Buster. ;)

Fang of Vog's regular attacks do pretty poor raw damage (see here), although they are able to inflict fire, which makes them a bit more attractive. Just as the whole point of Leviathan is its charge attack, so is the whole point of Fang of Vog its charge attack. People annihilate the Royal Jelly with it. People carry it into FSC, even though the fire is worthless, just because the raw damage of the charge attack is so high. To make good use of it, you want lots of fire protection and lots of charge time reduction.

I highly recommend getting either vortex. Even if they don't do much damage, the clustering alone will greatly help. Other than that you have most of the bases covered for bombs.

as for swords, why isn't faust on that list? You got leviathan yet not faust? The curse can be immensely helpful, and it has way more knockback than acheron, I suggest you give it a shot.