As others said, they wouldn't work in this game really.

To begin with, all classes need some solo capability in order to progress through story content etc. So there can never really be a full on support-only class.
In addition to this, you can give classes supportive skills but if they were to develop something that is solely focused on supporting.. What do you do when there is nothing to support?

I don't mean to bring this topic up but it becomes a bit like the healer DPS argument..
When everyone's health is topped off and there is nothing to heal, what do they do? Just stand there?

Same situation with a support class.. When there is no supporting to be done, what do you do? Stand there and tip your hat?

I wouldn't mind seeing another supportive orientated healer though.. AST was a good start with the card system. I could see how a RDM could have been a healer/support similar to AST, however I am a lot more happy that casters are getting some love as SMN and BLM have only been the two casters in the game since 2.0.. RDM seems to me like one of the better options for a caster that would mix it up a bit over and above what we already have.

So no, I am happier with their choice to make it a Caster DPS.