Yeah except it's doesn't... and I am playing a pure Mastery build (ILVL 346 at the moment). I don't see how that can keep a tank alive in M6 or higher and it really doesn't matter if you use HW or HS, both have similar values. In emergency situations the crit chance on a buffed HS is just a lot more reliable than the faster (but slightly stronger) HW. The base value for our spammables is just too low and even with Mastery in a lot of situations it's luck if the tank stays alive or dies (other group members CCing, tank using CDs or self heals etc.). In a group that's playing together for a long time this synergies exist but besides that... I'm very sceptical. You're just spamming Riptide -> HS/HW -> Riptide -> HS/HW -> HS/HW etc. and it barely heals for the damage a tank gets in that situation. Again, maybe all of the healers struggle with this (although I think Monks have the best way to counter it with Enveloping Mist which is incredibly strong with its 40% healing buff on the target).
The thing is, "high" group damage is easier to heal than very high burst damage on the tank imho. The easiest for me to heal are pure melee groups due to Healing Rain / Wellspring etc.