H8's prime strength is that he's modular, and as a droid is immune to some of the nastier force techniques.  His big weakness is that he can't lightsaber duel any force user more powerful than an initiate, and his poisons don't really work on force users, so she's more at the mercy of others than anything else.  Don't think that body you see before you is the one with the holocron in it though.  ;)