Vihermaali

In my opinion, that is one of the mistakes that usually leads to sentinel tank death.

As a priest, when healing sentinel tank you must spam max rank greater heal non-stop. You have time to regen between sentinels. Why spam non-stop? Sentinel can do almost 24k damage in 2 swings: 10,5k first swing, 3k pulse, 10,5k second swing. Time between swings: 2 seconds.

You can't really afford to do low-hp/sec global cooldowns like casting prayer of mending. What if sentinel decides to do the burst just as you cast prom? Tank dies because you are FOUR SECONDS away from landing next heal (1,5sec global cooldown + 2,5sec GHeal cast time), that's up to 30k+ dmg done on tank before your next heal lands.