I believe that Barbarian and Monk have a 30% damage reduce, while others (Witch Doctor, Demon Hunter, and Wizard) have nothing special. This causes a unbalance on the careers itself. As everything else is the same, why not choose Barbarian or Monk with bonus on the damage reduction?
Each career should has its own special bonus that can separate them from others. Not just as simple as now. My suggestion is:
Barbarian: 30% Damage reduction. (Barbarian is typical melee, damage reduce is acceptable.)
Monk: 15% Avoid Hit bonus, and 15% Damage reduction.(Monk should not be the same as Barbarian. As Dex is the key, may be Avoid Hit bonus is good).
Witch Doctor: 30% Bonus on Lift (As it is “Doctor” why not increase the life for them?)
Wizard: 30% Damage Boost (Wizard can have high damage, increase damage is a good choice)
Demon Hunter: 30% Avoid hit (I know you feel this is too much, but in another word, if DH did not avoid the hit, he almost dies instantly.)
And in this case, each career has 30% bonus on different area. And will make player to have a balance choice on different careers.
Of cause we can have different bonus too, like movement speed, critical hit change or others. But really we need a way to balance them.