How do I defeat Fuad the Cannibal?

I just stunned him and hit him a few times then left the dungeon and repeated until he had no health! Health bars don't reset if you run away!

Fuad gets a health buff from his melee hits, so the trick is to stay away from him. Use whatever abilities you have to kite him.

The solution to defeating Fuad is indeed using a freezing/rooting/stunning attack to keep him rooted in place.

I'm running a Demon Hunter build, who was level 18 when I found Fuad, so avoiding melee has already become second nature.

Using Impale with Impact put some stun on my right mouse button. To keep the high damage and to generate hatred I laid Hungering Arrow with Puncturing Arrow on the right button.

Caltrops with Torturous Ground worked very well to stop him when the Impale failed to ... if you're not level 18 Hooked Spines works fine as long as you're using reasonably fast weapons.

Vault with Action Shot lets you keep throwing arrows at Fuad while you're dodging his Melee attacks.

Evasive fire helps to add some movement away from Faud, but with how small his room is, this if EF fires off you're already in trouble. Still it might save you from time to time.

If your class has a blinding skill,you can step in,use it,lay down some damage,and then back out while the cooldown refreshes. Thats what I ended up doing because the monk is a straight melee class with very little in the way of ranged attacks.