The new glamour system is a shortcut to the traditional glamouring, nothing more or less. You can have different look for your three tanks, but it needs you to a) put all the glamour items to glamour storage or use armoire items. B) create one plate for each of your tank job and C) apply the correct one each time you change job. That's is because what the new system does, is just apply the plate's content to your gear exactly as if you applied it by hand. And for different jobs, it just offers shortcut to what you could do before, appply a new glamour every time you switch jobs. Why your glamour liked to be reverted is because you might have use artifact (DRK only) gear for the glamour, and normal behaviour is to show the default armor look if the current class can't wear the glamour item.