Well monk is a really high skill cap. You have to be good to play it. Warriors you have to be good but not as good. The dps of the two is different. So is the tanking. Dps of warrior is pretty straight forward folloe a rotation watch rage. With monks you have to keep certain buffs up while being mobile. Tanking on warriors is sword and board like anyone would expect but monk tanking is active mitigation so you need to be overly concious of mechanics.
Warlocks are really fun and revamped and intersting. Demonology is a blast to play. But mages just run through people if their good. Regardless of gear.