post-Dawntrail even story dungeons are harder and more punishing to heal than ever

[Granis]

You can freely move with eukrasia, I don't know why pressing a button while moving is an issue. Also, holos, panhaima, haima, physis, ixochole, etc. SGE has a tone of insta cast heals

yes but consider this:

finding the button and clicking on it takes time, while you're also trying to orient yourself and move in time, if you're using the mouse to both click on buttons and for camera control as you used WASD to move, clicking even instant cast buttons might cause you to die if the AoEs are too fast or too punishing. I typically find i can only toss out my instant casts towards the end of a movement phase for this reason, and because the boss does this 4 times in a row, there isn't enough "breather room" to use any abilities until the mechanic is over with and someone has probably either died to the aoes, the poison dot, or the spread markers.