Casters and healers will be standing directly behind you on Asira Dawnslayer. Most tanks will move from side to side, turn to face the boss away from the group, and normal good tanking behavior.
On Asira, this is wrong.
Stand between the group and the boss, and give yourself a LOT of room to back up. When she puts down smoke bomb, back out of it calmly, and get her out of the bomb. If the casters are standing behind you, then Thrall will pop totems down behind you or in that area. You will need to do little movement, and more importantly, you won't be kiting your healers or causing a loss of 75% healing and dps through constant silences.
Any movement more complex than this is a fail. This is the easiest way to tank the fight.