I switched from Rogue to Monk (Played Monk in early WoD). Assassination has been pretty decent numbers wise, and not awful to play but the lack of on-demand aoe burst has been a problem in mythic. I was still doing good damage because our ST was very strong, but it didn't feel all that great to play once they made Outlaw useless. Subtlety is theoretically good but I can't find anyone making it work well.
WW has been considerably more enjoyable to play. It isn't punishing and you excel in several different situations. The main drawback for me has been dealing with the lack of Cloak of Shadows, though ToK is a pretty strong cooldown in its own right. Not having to micro-manage a bleed/DoT is refreshing and most of your abilities feel very powerful, which is fun to play, and why I preferred Outlaw to having the majority of your DPS come from bleed ticks and passive poison procs.