I found a neat combo.

>Psyker's Breastplate from Kasballica
>Awakened Nightmare from Fellowship of the Void
The sword increases veil degradation.
Veil degradation increases perils chance.
Perils increases psy rating.
Psy rating increases everything.

Because you're going to be maxed out at 20 veil, you're essentially getting 20% extra damage per point of psy rating. If you're spamming psyker powers you're going to be stacking 3-5 extra psy rating every turn until end of combat.

I don't need any other gear that increases psy rating or dps anymore. These two items alone catapult you into hundreds of damage. This is great for my solo run because it means I can devote all my other inventory slots to survivability.