This is a misunderstanding of the tank/healer problem, in that it is not a tank/healer problem at all.
It is a scaling problem.
If higher tiers didn’t randomly not only one shot but vastly over one shot tanks that did not have a CD up, then healers could and would be useful.
High end groups have always looked to speed up fights, which even in TSW generally meant not having a healer.
However completing the content with a normal setup was actually viable, and the “lets push max speed” way was generally more prone to failing if not done correctly.
The opposite is true in SWL.
While a healer/tank can theoretically function in the high end tiers, the higher you go the less stable it is, and in 9s and 10s its basically a roll of the dice if the tank is going to just fall over.
Honestly sometimes it can even be a roll of the dice even with a sustain tank if timing is off.
Which actually brings in another negative of the current situation.
With sustain tanking being largely “the way to do it”, even in lower tiers where its not really as necessary, it does somewhat limit the number of people tanking.
While it seems relatively simple to me, I am aware not everyone is super comfortable having to constantly rotate their cooldowns with precise timing, on top of the other normal things a tank has to do. Those tanks that would like to run with a healer often run into a wall, and that can be frustrating and cause people to just stop tanking (or even playing).
However the solution is to fix the scaling issues, not introduce further complications.
As I understand it the current biggest issue with actually fixing the scaling problems is that, barring a different scaling solution entirely, they would have to be hand tweaked, probably per encounter per dungeon, which… ugh… understandable why that method has not been done.
That said, hand tweaking to the scaling has already happened on certain fights, both during beta of the dungeons and after. Mostly adds.
Because if you think the boss encounters suffer from linear scaling issues, holy crap the adds scaling was so much more broken.
Even to this day it often feels like the 2 adds between DW1 and DW2 are more of a boss encounter than the bosses.
I completely understand and sympathize with the healers dilemma, but the tank is not your enemy.
… well …
maybe the tank commander is.