From 250 hours of play perspective.
First flaw is the weight system. Currently, it’s too difficult to be firmly in the Light and Fast segment of the scale.
Second flaw is putting the re-spec system behind the Crucible grind. In my opinion, there shouldn’t be a need to jump through hoops to access a re-spec mechanism. Once you reach max level, re-spec should be available. Gaming is first and foremost about having fun. We should be able to experiment with different builds without being forced through a procedure, that for many of us just isn’t fun.
As I said in the title, it’s a fabulous game. Address these two elements and you’ve got yourself an awesome game! 