Balance is what got us where we are though. They are so balanced, they have more or less the same tools and features with a different coat of paint.
They have tried that sort of thing. But it can have the reverse effect and make healers avoid PF because they believe they shouldn't have to heal people's mistakes and that they should not make them, even if mistakes are part of the design of the fight.
The bigger issue isn't healers getting used to it, but gear making it trivial so that after some weeks they may not need to care about the heals and mit as deeply due to higher HP pools, defense and heal potency, including of the barrier tanks. So some healers might never actually experience how tough the healing was in the first weeks.
Boss auto attacks will suffice. And they have been doing these more in recent content. The issue was all these "larger than life" casts meant bosses were too busy to actually auto anymore.SE could use random raidbusters / auto crit but it was already that in ARR/HW
Removing that from both tanks and healers would be a start. I don't know how it would work with the scaling at level 100, but the trinity was clearly more intact back then whereas now, even in an Extreme trial a tank can keep the party going for ages after the healers die so it can be finished off (I did this multiple times the last week).Remowing OGCD healing could force experienced healers to do more gcd healing, but give the feeling of healing like ARR / HW
Old content wouldn't be harder, but rather easier, if there were more attacks dealing higher damage. And old content does not need to be any easier. It's in a bad spot as it is.This is a way to make healers more engaging for experienced healers without hurting the game too much and its design (that is based around damages), only issue would be old content, having a few more damages buttons can be easily fine, but actual caster rotation could lead to synched old content being harder
I think the best hope for this is if they do something like skill trees in 8.0 like they've talked about.