So I guess there are three consistent responses in this thread. I'll try to address them again here.
1) "You were a crappy healer before for not having 50CNJ."
I ranked THM prior to 1.18, and my main is ARC. (If you can make an argument for why healing THM needed 50CNJ in 1.17, feel free to do so.) When 1.18 came out and THM was relegated to RDM status (i.e. secondary healer), I accepted that, just as I accepted ARC's nerfs in 1.19. I ranked up THM in the first place because it happened to be the best healer, not because I wanted to main heal. I'm fine with it not being mainheal, but I still would like to keep a healing job.
2) "Just level up another class instead."
As I said before, if you believe that "Just rank up a different class for the same role" is a valid response, why not just do a character wipe? Isn't the point of not doing a wipe to prevent the reduplication of effort that players have already spent?
3) "You should have expected big changes."
I'm fine with the big changes; nowhere in this thread have you seen me ask that THM maintain its role. But nowhere in the scope of "big changes" is it implied that they cannot allow plays to reassign levels based on the new roles that they assign to classes.
I'm really surprised at the amount of vitriol this suggestion has generated. What is the downside of allowing players to reassign levels when major class roles are completely reworked? Is it that players will be able to reassign the time they have already invested to the new roles SE has created? Whom does this hurt?
You're acting like I'm asking for a perpetually available reassignment ability. Giving the players an option to reassign levels when they completely change roles around is completely fair and reasonable. If they radically changed crafting so that WVR and LTW no longer made any finished gear (which was all made by ARM), I would be saying the same thing.