Given that off tanks are being reworked into DD if 1-3-2 happens, that would basically mean that the concept of off tanks would no longer exist and that any tanks remaining would be just (main) tanks.
Based off what Mr. Kaplan mentioned:
Now, if barriers are going to be reduced even further or are totally gone and everything else remains the same i.e. damage numbers are not reduced and healing numbers are not increased, then the Support players are just gonna be placed under so much stress trying to keep up as well as experiencing an increase in heckling by angry team mates.
Not to mention how the (few remaining TRUE) Tankers would feel having to relearn how to play a character whom they had been regularly playing.