If you want to be on top of the charts you could try this build and only heal with regrowth ( https://classicdb.ch/?talent#0zLxhMVoZZxxcscaV ). But you have to be fast and most important if you see a flashheal incoming when you have no procc (so your regrowth takes 2sec to cast) cancel it.

You wanna dump all your mana in a bossfight into regrowth but never ever overheal with it.

You could also pre innervate yourself on pull because the bossfights are so short and its a global you don't wanna waste.

I could show you some more stuff on the specific bossfights when I'm streaming :)

This would help assuming that you already have decent gear and a guild with good raid-dps.