I haven't played Burg for a while but rolled one on Treebeard, so pardon me if I missed a discussion of this mechanic in a recent update.
Why do Gamble skills overwrite high tier version of their effects with lower tiers? One of the most frustrating things I've seen is when I manage to get a T6 Gamble of any color on an enemy only to use the skill again later (unintentionally or otherwise) and have it be replaced by a T1 Gamble.
It would make much more sense for repeated uses of Gamble-applying skills to tier up their effects on the target and/or refresh the duration. I know I can be more mindful of when I have a T5-6 effect and not overwrite it, but I think it would make Burglar a little more reliable for DPS or debuffs if we could intentionally increase the power of our effects by using skills intentionally.