Im very tired of this myth of mastery being a bad stat, so let’s stomp out that rumor real quick from a m+ perspective.
Mastery as a stat is not useless in the slightest for “fistweaving”(which is an outdated term but we’ll keep it around for arguments sake here), and there’s several reasons as to why. One of the most important is how it interacts with both of our major cooldowns. For revival, it gains a bit of a punch, which it desperately needs now in a 5 man scenario, and mastery helps getting there. More importantly, Chiji takes on a whole new form when gaining any decent amount of mastery. We already saw this in season 3 of Shadowlands and the potency of call to arms. In some ways chiji rotations began to branch into sustain and burst depending on the amount of mastery you had at the given moment(burst allowing for chiji gusts to fully heal party and sustain allowing enveloping mists to take control on rot encounters).
But to many thats not enough to even consider mastery, as it doesnt contribute to damage directly or our heals that branch off from damage, chiji aside. However what it does allow is access to more dps uptime and less cast time and more mana efficiency. Of course mastery won’t help with ancient teachings maintenance but what it will allow is a faster recovery rate from needing to spot heal → back to maintenance. Once again we saw this in practice with call to arms, as the latter 12 seconds of woo allowed for bursty heals from heals that would not be potent without it.
So in reality mastery may seem like a poor choice, however because of its interactions with several portions of our kit, it’s in a good spot. And if you need any more evidence you can gladly go check out my success from s3 or mymiro’s success from s4.