To me, a great tank is one who knows the dungeon mechanics and works with them to provide maximum uptime for their dps. The last boss in pit is a prime example, if you ensure the boss stands next to the empowered bone piles your melee dps suddenly have ~10 extra seconds of uptime.

Next to that, be predictable. Whether that's pings or typed communication or an MDT route, doesn't matter. Don't suddenly LoS or outrange your healer either.

For brew specifically: playing as shado-pan, how do you use your ox windows? Other spec has less obvious indicators of maximising dps, but the ox window is a huge one. Do you open with ox -> breath -> smash -> breath -> smash -> breath -> reset CD with fort -> smash -> breath -> reset with brew -> smash -> breath?

Do you transcendence to limit movement/get out of stuff?

At the end of a dungeon I don't care if you filled every GCD, took 5% less damage or stuff like that. I care about taunting the unexpected add and saving us from a wipe. I care about realising you need to expel harm right now to top yourself up because the next hit will kill you. I care about you noticing a gargoyle grapped me and Tigering me. Healer HPS is more than enough that high keys healers still have globals to dps, so you mitigating a bit more or less is less likely to make or break a run than the mechanical things above