Protection Warriors :You can use your Last Stand and Rallying Cry for yourself and allies to have massive Fleshcrafts before the timer as well. This is great for every dungeon, and by the end of the first pull your fleshcraft should be off CD anyway. Nice way to add an extra 50k HP buffer when you're feeling out your PUG healer's capabilities :D
Boon of the Ascended to get the Pelagos mastery buff at the start also works (you can also collect the orbs that prolong the buff).
Not sure if it still works but in BFA you could cast soulstone on somebody before the key starts and they would keep the soulstone buff while your cooldown would reset.
Feral Berserk effect actually disappear when mythic start :c
How does the interaction between IQD and Bloodlust work? Does lust affect other buffs in a similar manner?
some people RLY need to start reading with understanding...
You can also pre-pot before the dungeon starts. This is useful in HoA, DoS, NW, ToP, SD and SoA because you're pulling things at the start
Adrenaline Rush is cancelled on the start of M+