Game balance is a delicate process and almost impossible to get right.
Whatever the method, the classes need to be balanced because
1) outside of a few masochistic players like myself, no one likes playing the "weaker" classes
2) while the game isn't competitive now, it will be when ladders go Live. In the game's current state, you'd probably be looking at ladders full of wizards. Some will be there because the enjoy the class (like I did in Vanilla) and the rest will choose the class because they want to remain competitive (regardless of whether they enjoy it or not.)
You can raise the other classes up or bring the dominant classes down. Personally, it makes little difference to me. I'm more interested in making sure that each class is unique, has interesting abilities, and is fun to play. From a mechanics perspective, I see little appeal in playing a Demon Hunter as opposed to a Wizard / Witch Doctor. For melee, I feel like Monk is the most interesting of the three classes.
Right now, I've been playing my monk and slowly bringing up my crusader. I just unlocked Seven-Sided Strike - wow does that skill feel good. I really enjoy the mobility and power of the class. That said, where my petless witch doctor didn't come close to dying until Act II (Waller, Arcane Enchanted), my
Monk regularly dips beneath the 50% mark even in Act I. I've started equipping both Blinding Flash and Breath of Heaven to help combat this. Should be interesting to see how long she'll live in Hardcore.
On a side note, I've really been enjoying the dialogue for the Crusader and the Scoundrel. It probably would have been really easy to make the Crusader your typical righteous paladin type, but she's been surprisingly down-to-earth and funny. The scoundrel has some great lines though and his company has been refreshing after sticking with the Enchantress for so long.
I think right now I enjoy the Monk and the Crusader the most. I really want to like the Demon Hunter, but her skills feel too lackluster. I don't need her to be all flash, in fact I like characters who aren't gifted with some extraordinary power, rather they tackle each situation with wit, speed, and tenacity. Vaulting is a lot of fun. Her generators and spenders are just not that interesting. :/
Witch Doctor on the other hand has a lot of great skills. I just can't play her the way I want to until she gets higher leveled. Also, I'm not a fan of her dialogue. I like Witch Doctors and all, but I don't feel like they really nailed her script. Maybe I need to play a male Witch Doctor instead.
Just my thoughts.