ToME: the Tales of Maj'Eyal

Is there any classes they are good for?

Chronomancers and Defilers come to mind.

Sun Paladin for sure, I've heard Berserker, Brawler and Cursed as well.

Necromancer is okay because you can heal your minions and your first racial synergizes with Blurred Mortality. Ghouls can also work on classes that can get 50% stun resistance, because Ghouls start with 50% base stun resistance.

Ghouls make fantastic paradox mages, and I won't comment on Ghoul Temporal Wardens as I have no experience with TWs in general.

The huge hp mod covers a paradox mage's lack thereof, and Celerity and Dimensional Step help to alleviate the Ghoul's global speed penalty by providing move speed & unparalleled mobility, respectively. I've heard that Retch + Redux'ed Ashes to Ashes makes for one hell of a field of death.

Another cool effect of the Retch is that it's a regen field for anything that is undead (you included), making it brillant for necromancers that will have only undead minions.
So basically you heal them while damaging the living enemies they're fighting inside of your retch zone.

Though if the enemies are undead, it can be a problem and you must be cautious of where to use it so the effect hit your minions but does not do the same for their opponents

Corruptor. Flames of Urh'rok cancels out their speed penalty. Ghouls have leap, which helps with corruptor's limited mobility. They have retch and blood grasp for healing. And lots of hp.

Also on top of that Ghoulwarks bring sexy back.

If you like addons, Ghouls make fantastic Flensers, from Doctornull's class pack.

Also, that prodigy that sprays blight and heals you for damage done is an amazing combo with Retch, especially on a Blight-themed class - it's very close to as effective as Cauterize for keeping you alive, and it has the benefit of killing any nearby enemy, as well.

edit: actually, i convinced myself.. time for a ghoul Reaver

I just won with a ghoul Cursed… rough start and again, a rough middle, but once you settle in, the thing is a murder-factory.

The only thing that stopped me is Atamathon and that's largely because I just hate trying to take him down so I don't bother.

Healing is your big issue for most of the game because you have no direct heals. Thus, Shielding runes are very important and I unlocked the warrior class with vitality in it, which helped (and also helped deal with status effects).

Still, once you get a good weapon (blighted maul was what I used) you can easily end up dishing out 750-1600 damage per attack, which is pretty sick. I'm sure you can get it significantly higher but I'm not inclined to the kind of hyper-detailed stacking that is required to do that. Honestly, I just want to play a game, not solve math equations.

Still, if you're playing a ghoul then I highly suggest trying a Cursed… if you can get out of the starter dungeon, you'll be in good shape.

Also, take the heart of the sand worm to the altar near the Grand Corruptor and it'll become the corrupted heart of a sand worm… that gives you vile-life which has two really good skills, the first two.

Good luck!