1. Rogues always been a simple class to play in PvE with the exception of sub rogues ( Which is still fairly difficult ), can't have affected population as they have always been that way.
2. That is the case for every single class getting a legendary, not a case specific to rogues.
3. Rogues have always excelled in 1v1, but guess what? The game is not balanced around duels and world pvp.