Funny, a "cleric stance" is implemented in other games and the sky doesn't fall.

Here's one such example https://aion.fandom.com/wiki/Sacrificial_Power_I.

So, how is this skill used? It's a toggle, it activates instantly, if you want extra DPS, activate the skill- however your heals (all of them) get decreased by a certain potency (if I recall, it was around 20%, maybe slightly more). You want to go back to full healing? Hit the toggle, you're instantly back to full healing power - but there's 10 seconds in between hitting the button.

Did anyone ever die due to "oops, I hit the button" ? probably- but somehow, this skill lasted for at least 10 years- so how much of a problem do you think it was?