Originally Posted by
Gnull
I think Rogue popularity is primarily to do with PvP.
When world PvP was still a thing, being able to stealth into enemy areas and gank people was amusing. It also provided you with some safety from being stalked by the opposing faction while trying to quest.
Now, you have two semi-viable PvP specs: Assassination, which has good damage but poor mobility, and Sub, which has good control and mobility but lags on damage outside of SD. Very few people seem to play anything other than Sub at high-level PvP- which could mean only Sub is good, but definitely means it will be harder to find a team that will take you as something else. If you don't particularly like Sub's playstyle, your options for PvP are pretty limited.
Over the years there have been 1) nerfs to Rogue damage and control, 2) specs that were non-viable for PvE or PvP for extended periods of time, 3) ongoing complaints about the fact that Rogues bring less group synergy/raid utility to a group while not doing any more damage than a hybrid class or a pure DPS class that can provide some kind of a group buff or swap roles on different fights, 4) irritating bugs with Stealth and Vanish that made core defensive and offensive abilities unreliable in random situations, and 5) continual complaints about the high cost of switching targets because of combo point loss and poison stacking. All these things tend to discourage new and existing rogues.
Rogues were also arguably OP in Vanilla- one reason why they were so popular- and then got the stunlock style of play nerfbatted hard, along with damage for some specs falling off the chart. They really haven't been FotM since. Most other classes have had at least a few FotM runs, at least on certain specs- Paladins, DK's, Mages probably racking up the most.
Rogues also have a pretty high skill cap. There are a lot of cooldowns to manage, and a lot of success as a PvP Rogue lies in very carefully timing stuns, interrupts, and cooldowns.