TLDR Right at the top: Healers are there to manage raid HP. Healers should have the raid cooldowns. DPS should be there for a singular purpose, to DPS. Tanks can have raid CD’s, but most cooldowns should be on healers only. Each healer should have an equivalent cooldown (a throughput CD does not equal a damage reduction CD).
I want to note that this is a PVE Mythic standpoint, and is not factoring in PVP oriented balance. The topic here is PVE, keep that in mind.
Healers are there to micro-manage HP of raid members, and should be the single focus of raid cooldowns. Some healing classes are devalued due to the lack of a mitigation CD, as damage mitigation CD’s are significantly more powerful than throughput cooldowns. Paladin, Shaman, Disc Priest all have mitigation cd’s, while Resto Druid, Mistweaver Monk, and Holy Priest (lolholy) only have throughput CD’s. The idea here isn’t to ADD additional cooldowns to the game, but to give the mitigation and throughput cd’s to the classes that are there to keep the raid alive. Shuffle the cd’s around (with renaming, things of that nature) to the healers, and maybe tanks if deemed viable, and make the cooldown portion of healers more fair and balanced. Healer balance will always be troublesome simply due to mechanics, absorbs being OP, etc but the gap between healing comp viability can be bridged by giving each healer an equivalent cooldown.
As of now, Mythic raids will be hard pressed to consider a throughput oriented healer in a 4 or 5 heal setup as damage mitigation CD’s become more valuable the fewer healers you have (unless monk are 5.0 status doing a large portion of healing over the other healers). Without somewhat sizable changes to existing healer balance, monks and resto druids likely will not be as feasible as a Paladin, Shaman, or Disc Priest is. If you give each healer ONE raid mitigation CD and ONE throughput CD (or just one mitigation cd, no throughput) this can help bridge the gap and level the playing field for healer class balance. This also directly impacts your dps raid comp as you are able to bring DPS for their viability in specific mechanic situations (adds, no adds, multi target dotting, single target patchwork fights, so forth) rather than picking a rogue over a mage due to the raid mitigation cooldown they provide to the raid on a boss such as Thok.
Just my thoughts, but I feel Blizzard should seriously consider removing raid cd’s from DPS classes, and focusing balancing healer cooldowns so everyone is on a level playing field. Throughput CD’s unfortunately do not match up to that of a raid mitigation CD, they never have and likely never will. There are advantages and disadvantages here, but I feel overall healer balance would be improved by reallocating raid CD’s around to just the healers (or healers and tanks). This is purely from my standpoint, and my opinions may differ from others. Curious to see what the rest of the community has to say in regards to this.