Ok, I like the Barbarian path. At first, I was looking at the attacks for Form of the Beast and thinking to myself, "Well, those SUCK!" And then I read the riders to the various attacks and changed my mind. Not bad! Bestial soul just gives you a few new movement options, but otherwise doesn't stand out. Infectious Fury is just fun! And the capstone? Holy &%$! You can turn your allies into Barbarians? NICE!!! Someone mentioned adding the ritual Speak with Animals earlier...I agree. Verdict: I'd play the hell out of this!
The Mercy Monk feels...weird. I am not keen on the mechanics, and as mentioned earlier in the thread, the cloud of fart just doesn't seem to mesh well with the concept. Verdict: I don't like it very much.
The Paladin: a few good Oath spells, but most are duds (Counterspell looks good at first, but remember that for every spell you counter, you lose a smite). Their Channel Divinity almost seems too strong, so I would have to see how it plays. Their aura grants a bonus to Initiative, which is nice but not over-powered. Vigilant Rebuke seems a little weak for a level 15 power; I think it should do damage according to spell level, but that's me. But it's capstone? Now THAT'S a capstone ability! Smack a creature not native to the plane you are on, you banish them? Holy Crap!!! Verdict: Not too shabby!
The Warlock: I'm not keen on the spells...they just don't feel very elementally influenced. Collector's vessel seems very Meh...there is some mechanical effect that can potentially be nice, but it's mostly just...meh. Elemental Resistance is a little on the boring side, but still useful. Protective Wish...uh, I'm not so sure about this one. It could be useful if you could tether an unwilling creature, though. Genie's Entertainment is a weak Maze spell, but it's not terrible. The capstone seems pretty weak, though. Verdict: Not impressed. The subclass suffers from not knowing what it wants to be.