Trying to answer my own questions on test. I put 120's scrolls on a CU: healing, anatomy, parry, wrestling and feint, with repel. Boosted hp, mana, regeneration, resists to max allowed. The CU was trained up 117/120. I tried it against a balron paragon in the blood dungeon and it could kill it with veterinary help in about 12 minutes. Can kill greater dragon with veterinary, can kill renowned mini champs in SA with no help. Can kill lich lord in 3 hits, no damage, kills most stuff easily.
At regular spawns, Cu's DPS too slow to advance very much. Can it take down a serious boss, dunno.
What would be a good test of it's tanking skills? I am too lazy to farm peerless keys. @ Archnight Dread warhorse, don't have one or I would try. I do have a dread mare I could test for you.