Can't really speak for PVP but in PVE, specifically dungeon content, Mistweaver is great. Monks are very mobile, between Roll and Tiger's Lust it's easy to keep up with every tank spec, even Druids. Monks have a decent mixture of insta-cast abilities/talents and channels, so you can spot heal a tank while they're doing a massive chain pull before you have to plant and channel. Roll, Tiger's Lust and Transcendence give you lots of mobility during boss fights. MW also has some pretty decent "oh shit" buttons for varying degrees of severity in Thunder Focus Tea, Essence Font, Life Cocoon and Revival.
Took me a while to wrap my head over Legion MW but it's fun.
MW has always had the ability to quickly turn all of its mana into a massive burst of healing. Works great in dungeons when you can drink after every pull, but they have a hard time on long fights because their entire toolkit is so expensive.
Also, am I crazy, or is the MW artifact ability kind of pathetic?