Someone else already summed it up perfect: Burglar skillset is just plain ineffective. Gambler is tedious and unreliable. MM I commented on above. I really do defy any Burglar that is "destroying" creeps with their "epic" Gambler debuffs and MM CC to post some videos of it.
Burglar progression does not match that of most other classes over the years. It's obvious Turbine has no idea what the hell they want to do with Burglars. It's very frustrating to go from God-mode to tissue paper within the course of single updates. Believe it or not, most Burg players would prefer the middle ground and then be left the hell a lone. It's a very fun and unique class that I think will sadly be ruined once Turbine "updates" them by removing all the intricacies they can't seem to balance anymore.