Well, it's a diamond so it's supposed to be hard.
Vampyre is probably the best build, as MBm with fists is nearly useless and MMB doesn't give you damage boost through berserk to use your fists efficiently.
About special levels - depends.If you think rewards are worth it, then go ahead.HA can be useful.CC is free healing(don't forget 4 HKs though).Halls are easy, i would recommend skipping everything after it, except maybe pits if you want lava element.