For example, Mercy and some other bosses were bugged for a long time and didn't drop their designated gun, or only dropped it in Normal Mode. The only specific rate changes that I can think of were increases, of one sort or another. I would like to think that they wouldn't decrease the rates, since they were already way too low for most people. It's always possible that they changed the rates without announcing it. I don't remember hearing about any general drop rate changes.
It may have a very small, indirect, effect, but you're probably much better off using any relic that makes the game easier for you, and may speed up the process of playing the game. The consensus is that the Vault Hunter Relic has virtually no effect on the drop rate for legendaries.
