He's not overpowered but he's certainly not representative of the character we see in the film. This is another unfortunate consequence of writing the rules based on an unfinished script, I guess Dori was originally meant to be a bit more of a powerhouse but that doesn't come across in the first film. HIs special rule is similarly confusing, there doesn't seem to be a particuarly strong bond between he and Bilbo during the first movie that would justify that rule.
Who knows, maybe in the first half of DOS (which was meant to be in AUJ when the rules were written) Dori becomes a combat monster who loves Bilbo!
He's certainly awesome in a Thorin's Company list though, he would be the 5th dwarf out of the 13 I would take!
