The gloves belt shield combo isn't as good as it sounds, plus the main damage in higher player count comes from corpse explosion, nova is just good for killing the weaker monsters so u can CA them.
I recommend 125fcr
Infinity merc
Buy some cheap eth insights to transmute them into iron golem so u don't have mana issues
Skill-wise:
max nova and it's synergies
only use amplify curse, don't bother with lower res curse
max corpse explosion.
1 point into all the summoning stuff if u like having some skeletons and revives around occasionally, mainly to prevent ur golem from being targeted too often so he doesn't die.
Rest in bone armor
Nova is killing on p8,corpse explosion is garbage on higher player counts....taken muiltiple necros to 99 in d2r. on p8 you use 0 summons to max the psn nova dmg.