I know we got different vamps with Dawnguard, but I mean powerful ghosts, liches, zombies, wraiths, etc.

I haven't played through much of Dawnguard yet, but I am assuming there were little to no summons added besides the gargoyles? (don't answer)

Anyway, I want more.

There were two new enemy summons. I won't say anything beyond that.

I want more necromancy. Pertaining to Dawnguard OP, you may wish to avoid ---->

are you sure you don't want an answer? all i'll say is yes there are more summons, and i don't think you'll be dissapointed.

Ok, sweet!

But I still want to fight more types of undead besides Draugr. I got my fill of them in Bloodmoon.

There are some new undead you can fight in DG.

there are new creatures but i don't recall any of them being undead. except for one area, but that's kinda quest specific, they don't cross over into the main map.

This. You don't encounter them outside of a specific area.