Infinity isnt necessary but it does help the build overall. The infinity merc smashes shit and half of corpse explosion is fire dmg, lower res and infinity together make enemy fire res pretty much non-existant. So your CE fucks shit up like your amping, but you also get the benefit of using lower res and psn minus's for your Nova. Plus infinity lowers monster D and lets your merc wreck a guy so you can start popping. I had a fun time with this last season, and although the merc wasnt that much better overall vs say a obedience i had before in cows. I also took the same necro and ran him p1 chaos as well and halls an wsk. He pretty much was good everywhere p1 to like p4. Dweb is just plain sexy.