For the life of me, I can't remember if Soulmancer changed it so you don't need a corpse to cast skeletons. I don't think he did...whence case, skeletons aren't really your best bet for a summoner because during boss fights there are no corpses.
Your best bet for boss tanking is a solid golem (situationally dependent, some folks max Golem Mastery and then pick a Golem to max, usually Iron) along with Spectral Blades. Blades are great because you can summon 4, the recast delay is very low, and they tend to entertain bosses. Also, Death Knight is at least a 1 point wonder, if not more.
With this setup, you generally want an Act 1 physical merc with emeralds and max damage jewels filling her gear - your job is to summon tanks for her and keep her alive. Or you can attempt to go the psn/summon route, but since your title says summonmancer I'm guessing you aren't going poison. Some people will also recommend 5 or so in Amp Damage, and any spare points into CE, since it's great for trash. Depends on your style
$.02
