I only know Crush from WoW, so I'm going to attempt to relate the classes to those and see what it gets me for a recommendation.
Barbarian: Warrior, probably a two handed spec though maybe there are dual wield barbs? I've not heard of any yet so I'm going to say think of them as a 2 handed dps warrior except with still having the sturdiness of a tank. I've known Crush to play a warrior, but I recall it being a tank.
Monk: Enhancement shaman. Dual wield, some healing ability, pretty sturdy. I'd say it has some rogue tendencies with the speed aspect. So Enhancement shaman minus the totems and plus rogue speed.
Wizard: Mage/Warlock. I'd have said just the mage, but some of the meteor type spells remind me of the warlock. Plus there is the hydra option and such so some small warlock tendencies there. Not really a pet though so very strong mage comparison I would say.
Demon Hunter: Hunter without a pet. Obviously a demon hunter is stronger than that and has more abilities, but that is the general feel I get.
Witch Doctor: Troll warlock summoner. I specify troll because of all the weird things witch doctor's do. Throw jars of spiders. Summon a giant frog to eat enemies. Send out locust swarms. It's all very Troll feeling. Combine that with the warlock's summoning stuff and it's not too far off the idea.
I started this out thinking that I would recommend a Barbarian for him, but having typed that all I think I'm going to recommend a Monk. It feels like an enhancement shaman which I think Crush likes. I can see him really liking having the option to heal which he doesn't get with other classes. That said, I really wouldn't be surprised if he liked a barbarian and it does feel to me like it might play a little slower and so possibly be better for his wrists. I'm slightly swaying myself back to barb, but I'm going to stick with monk I think. My recommendation would be as follows.
Monk > Barbarian > Mage > Witch Doctor > Demon Hunter
Purely from my feeling for what Crush would enjoy not based off which class is actually better and with the Monk > Barb bit being a close call.
edit: Nobody saw me call a barb a bard... *whistles innocently*
Barbarian: Warrior, probably a two handed spec though maybe there are dual wield barbs? I've not heard of any yet so I'm going to say think of them as a 2 handed dps warrior except with still having the sturdiness of a tank. I've known Crush to play a warrior, but I recall it being a tank.
Monk: Enhancement shaman. Dual wield, some healing ability, pretty sturdy. I'd say it has some rogue tendencies with the speed aspect. So Enhancement shaman minus the totems and plus rogue speed.
Wizard: Mage/Warlock. I'd have said just the mage, but some of the meteor type spells remind me of the warlock. Plus there is the hydra option and such so some small warlock tendencies there. Not really a pet though so very strong mage comparison I would say.
Demon Hunter: Hunter without a pet. Obviously a demon hunter is stronger than that and has more abilities, but that is the general feel I get.
Witch Doctor: Troll warlock summoner. I specify troll because of all the weird things witch doctor's do. Throw jars of spiders. Summon a giant frog to eat enemies. Send out locust swarms. It's all very Troll feeling. Combine that with the warlock's summoning stuff and it's not too far off the idea.
I started this out thinking that I would recommend a Barbarian for him, but having typed that all I think I'm going to recommend a Monk. It feels like an enhancement shaman which I think Crush likes. I can see him really liking having the option to heal which he doesn't get with other classes. That said, I really wouldn't be surprised if he liked a barbarian and it does feel to me like it might play a little slower and so possibly be better for his wrists. I'm slightly swaying myself back to barb, but I'm going to stick with monk I think. My recommendation would be as follows.
Monk > Barbarian > Mage > Witch Doctor > Demon Hunter
Purely from my feeling for what Crush would enjoy not based off which class is actually better and with the Monk > Barb bit being a close call.
edit: Nobody saw me call a barb a bard... *whistles innocently*