Couldn't have said it better myself. It does somewhat feel like a slap to the face to me any time people try to use "Balance" as an excuse for why Tanks and Healers should never get any new jobs. "Perfect Balance", quite frankly, is a myth, IMO. It doesn't exist, and it never has.
If the developers decide that Tanks and Healers shouldn't be getting any new roles again for yet another few years via the release of the next expansion, I'm going to be very upset. Tank and Healer mains have already been forced to wait several more years due to Stormblood only releasing two DPS jobs. If I was in charge of how to release jobs in this game, and it was already agreed upon that there would only be two new jobs per expansion, I'd set it up as follows:
Odd Numbered Expansions: 1 Tank and Healer respectively.
Even Numbered Expansions: 2 DPS.
That's not taking the whole "What job would arguably fit as a Tank or Healer instead of a DPS?" thing into account either.
Thus, I absolutely hope that the next two jobs are a Tank and a Healer. I'm going to be miffed if I see another DPS job in the coming expansion. Because as someone who far more often plays as the Tank and Healer jobs over the DPS jobs, I too would like new toys to play with in my usual go to roles.
Now mind you, I just said I'd be upset if we don't get any new Tank and Healer jobs in the next expansion. I'll still be playing the game regardless.