summon necro
max in order - raise skeleton, skeleton mastery, corpse explosion. then, do w/e you want really. i don't use mages ever since they can freeze. i put 10 into golem and 10 into revive. currently level 90 and haven't been close to dying. put a point into bone armor, amp damage, and lower resists w.e you want (i did as soon as each was available to me)
items - leoric, lore, random amulet with resists + mf i found, smoke, homunculus w/ p diamond in it, trang glove, 2x random rings with magic find on them, verdungo's, and marrows
merc has insight in a halberd, hawkmail, tal mask
in hell i have max resists and can raise 11 skeletons with this setup (no anni, no hellfire). some people don't like leoric because of bone prison chance but if you do get stuck with a monster just decrep them until it wears off.
this build can clear any content but bosses are insanely slow and not worth it. cows, chaos, wsk, etc. all you do is amp and then cast corpse explosion once one dies. the radius is nice when it's maxed out and you can do a cow run pretty quickly even with the above budget gear