I haven't played Diablo2 in forever but if I remember correctly the best strategy with a Necro was to summon as many creatures as possible and essentially let them do all the killing for you while you stand back and peck at monsters with whatever ranged weapon you can equip (if you hold shift you'll stand in place while you attack instead of rushing at the monsters too).

Ya check your patches. Easiest and most simplest form of fixing!