Depends how you want to play. In a team, class doesnt matter too much for you can cover the other chars lacks and vice versa (heal + tank + fastkill, etc.).
If you solo, to my mind barb is quite safe but slow - all classes can solo the way to mq, but they are too different to skill / equip for a fast answer here.
Read the guides (basic), most of the answers are already given there.
Gl slashing,
Verdun