as a summon necro, more than gearing up for tankiness you may wanna work on your mana regen so you can spam skeletons to prevent 1 shot aoe stuff. of course dying is a possibility but if you are so worried you can swap to those magic absorb boots and a few magic resistance items for the task and then switch back to your original build. also you can kite him away, tp then run back to the cow to open the portal.