Camelia has better AC and lots of super useful buffs that Regill does not have. Her saves are better and she can make herself immune to most things. She can buff her weapon and heal and cast resists. Regill does do more damage, he is actually better as dps, he is better than Greybor at it.
Wolfjit can also drain strength which is btw mostly useless, you are better at using drain Constitution ability. Wolfjit can buff himself so he is also a decent tank, he does more base damage than Greybor and has same sneak attack and also get Debilitating sneaks attacks that Greybor does not have which both reduces enemy AC and attacks for him and whole party.
I wouldn't say any kind of stat drain is useless, it's free debuffs that come with doing what you would've been doing anyway. Unlike Camellia, Regill is nowhere near as resource dependent and resource burn is low key a highly important metric. Hellknights get
Triumph Force of Will which permanently buffs Reg's saves against fear, compulsion or charm. Fear effects become a non-issue with Remove Fear anyway. Camellia's got more tricks up her sleeve sure but then again self-sufficiency and versatility are overrated qualities in a party based system, which is why I'm not too fond of hybrid classes.
I would question the claim that Greybor does little damage, I have so far noticed no significant deficit in that area. Using Woljif's spell slots for all the buffs he needs to become melee viable is a huge waste if you ask me, nevermind the fact that he is only proficient with simple weapons unless you waste a level to give him martial weapon proficiency. Much like Camellia, Woljif is a lot more resource intensive than Greybor. Slayer not getting debilitating sneak attack is a bit of a bummer I'll admit but there are enough other abilities that lower enemy AC and in exchange he gets Studied Target and Quarry. I would rate Slayer higher than Rogue in general. He can't pick locks, but that's what ArushaBAE is for.