Yesterday, the drop-rates of legendary items in the game’s newly added Ultimate Vault Hunter Mode was severely lowered. Gearbox Software’s community manager responded earlier today that the loot tables are currently being worked on but this code wasn’t meant to go live yet. As such, the lowered drop-rates has since been removed from the game. Gearbox's official statement follows. "We’re always looking at balance tweaks on our internal server. Unfortunately a test string went live before it was ready and has since been pulled down."
This seems to imply while the code that lowered the change of finding legendary gear from Loot Midgets inside “Borderlands 2” might have been an accident for now, it seems that the developer is currently testing and looking at a permanent lowered change to find decent gear.