I've got Leviathan and Magma Driver right now and I'm wondering what would be the best choice for a third weapon, since I have 2 slot upgrades to use. I was thinking about going with Divine Avenger. Thoughts?
Also, if I were to get 2 trinket slots, do 2 Elite Slash Modules stack? I.E, will their Damage Bonus Mediums combine to a Damage Bonus Ultra?
To answer the first question - your weapon choice should be based on what you're going to be facing, and your play style. If you're planning on running the Firestorm Citadel a lot, then absolutely get Divine Avenger. For the Jelly King, you would probably want Gran Faust, Acheron, or Dread Venom Striker, depending on personal preference. I think you get the idea.
For the second question, yes, they do stack. Two Elite Slash Modules will combine to give you a Very High bonus. If you combine that with, say Barbarous Thorn Shield, you would have a damage bonus of Maximum. Keep this in mind when picking out your weapons, as with certain playstyles, you might prefer to get the other two modules instead. Like, say, if you want to spam the charge attack on Divine Avenger or Leviathan Blade, go for two Elite Sword Focus Modules.