Hello there,

I'm going to give my three different configuration here, so please check links below.

Blast/Corrosive for Plague Star Hemocyte/Lephantis | Config B
Cold/Radiation (+Slash/Viral) for Index | Config C

In configuration A, I created the most universal, pure Slash build, You will get Viral from Nourish, and Primed Expel Faction will highly increase your damage output. If you are not a fan of Faction mods, or/and you don't like to change them every time you pick a mission, just put [Hornet Strike] there.
Enjoy, THeMooN85