Healers, heed the caution in the warning.
A tank that strafes moves out of healing range rather quickly and unexpectedly or the tank can turn a boss onto you to take a cleave in a blink of an eye. Watch for clues as to determine what you have to do. If you see the boss or mobs head coming to towards you, backup and roll away from the face. If you see the tail end swing towards you, move up and away from the tail end, or stay at the tail end. Each fight is different so the onus is on you, the healer, to know the abilities of the boss\mob and move and position yourself correctly when a tank repositions a boss\mob.