i just made a necro and they do own all mele battles with bonewall bone prison and iron miaden, but when they catch on you will need lowwer resist and max bone spirit. Against sorces and amazons i dont know cause amazons are so out of hand now, the only way you can kill one is if you stand back cast bone walls in front of you while she fires thinks you almost dead runs up then you bone prison her cast lowwer resist and rape her with bone spirits. As for sorces you will need max resist cause 1 TS kills me so keep that in mind for your equiptment.

Bone spirit - 20
Bone wall - 1
bone prison - 1
lower resist - 15-20
iron maiden - 15-20
decrepify - 1-20 (im not sure about this only used decrepify once against a barb)
Corpse Explode - 1 just for cow runs

Thats what i have figured works for now hope it helps.