Here's a list of builds that IMHO have advantage over a random necro:

1) Maran anything is the best and easiest natural counter (with eyes). Bonus points for having cure blindness.
2) Hiders, best among them an assassin - you have surprise and can one-shot them, they can't do anything to you unless you let them.
3) Hero Scarab - they can't sleep you.
4) -50svs and up (especially on high-int builds) and no rank advantage go a long way.
5) Quality inventory and prep bag (cure blindness, teleport, return potions in inventory; cure disease/poison/remove curse in the bag). Admittedly, the worst defense.

Now, some/all of this doesn't apply against a power lich, but we don't have one ATM.