A pale master can specialize in neg energy, but doesn't need to. I have the shroud and the pet, and a little of neg energy boosting, but I also have points in EK and use a couple bastard swords. I have Archmage specialized in abjuration for the SLAs, but otherwise just took the extra SP and metamagic cost reduction.
I kill things with pet, blade, and about a dozen commonly used attack spells, plus cc spells. The sl 9 firecloud spell (I forget the name) for example is awesome, and the drow SLA darkfire is amazing too in some cases and ensures I have a hard hitting spell when "out" of SP.
Truth be told, killing things with neg energy is kinda rare.