Honestly I would be cool with the healing from it being toned down a little if it was a 1-1.5 min cooldown. AOE healing is littered with gaps for mistweaver and simply can not compete with most other classes in fights that have lots of AOE dmg going out in raid. SG is too slow to ramp up as well. It needs a base heal associated with it and not just be based on how many mist puddles are laying around or the healing per puddle need increased. If you only have 1 or 2 puddles available it does basically nothing.
Over all the gaps in AOE healing is such a headache for mistweaver to overcome. The kit is littered with too many small unimpactful ones that require too much preramping to be useful.
In M+ it isn’t bad because managing 5 people isn’t too hard but in raid it just falls off a cliff and it feels we have been relegated to dedicated tank healers.