I would say Fire, Dark, Electric, and Ice because they all have an AoE damage aura.  Out of those 4, I would choose Ice.  It can take the alpha the best out of those 4.  It will have the highest mitigation with a full group.  Then the -ToHit from DM will pair nicely with the defense of Ice.  Ice also has -rchg resistance, so you won't slow down hitting siphon life and most of all killing, although you won't be getting hit much anyhow with soft capped defense and -tohit, but those pesky Psionic hitting NPCs which slow recharge won't affect you much.