IMO planning is more skillful than reacting.
And the DPS comes from a healer that knows how to use CDs effectively to do it as fast as possible.
But here is the catch, by doing so you can balance HPS and damage on a 1-1 basis which would include downtime to dps. Today you cant. You can buff healers all you want, but once you reach 1-shot area more HPS will not translate to better outcomes.
But. I have to agree. Staggering damage, or applying a shield is just different sides of the same concept : Heal for 20s before bigD to make a shield, or heal 20s after the bigD to deal with the stagger.
Either way, it would be a solution to the healer throughput problem.
This is not an issue IMO. Its part of the healer skill in M+.
The issue is the unintended ramifications of not capping damage in M+ : Eventually, no amount of burst healing will save you. So much so, that having a healer in the first place is put into question.