I hate to admit it, but this is kind of right. At least to some extent. Damage has become so bursty and frequent that it’s made instant heals much more effective (at least in an M+ environment).
Mistweaver has Vivacious Vivification. I might even considering Soothing Mist into instant Vivify casts in the mix, as even though you’re channeling SM it’s allowing instant cast heals, and with how Renewing Mist works it gives a lot of passive/cleave healing. Not to mention that fistweaving in-of-itself is a lot of melee ability usage, which of course is innately “instant”.
Resto Shaman skyrocketed this season with Totemic, which automates (instant casts) a lot of free Chain Heals that they no longer need to hard cast.
Holy Paladin (AC Lightsmith) more or less ignores all casted abilities, instead prefering only usage of instant/melee abilities. And like MW, a lot of passive AOE cleave heals just based on how the toolkit functions.
Disc Priest, while still needing to plant to cast Radiance, is more often than not still able to do the rest of their heals on the go. Renew, PW:S, Rapture (RIP), Purge the Wicked, Penance, etc are all able to be used on the move. This coupled with an insane burst AoE profile this season every 20 seconds, plus their utility, has seen it ascend to the top of m+ pushes.
It’s little wonder that the two healers that have to sit and cast for a majority of their heals are Holy Priest and Preservation are also the least played in m+. Not only that, but their AoE heals are also limited to an incredibly limited area (Sanctify, Dream Breath), which makes spread encounters with frequent AoE damage a PITA to deal with. Thinking of bosses like AK 3, Mists 3, etc that are just brutal for these two healers to effectively heal through.
Not to mention the annoying frequency of high AOE damage whilst simultaneously requiring a lot of movement that unfairly punishes healers that actually have to cast (think Consumption, and to a lesser extent Gossamer Burst, etc.