I theory, this is great, however, in practice it is abysmal... What happens is you get a DPS version queue up as a healer, just to get faster queues, then refuse to heal as its "not their style." I've seen it happen in other games, and those forums are stuffed to the gills with threads asking for them to be removed.

The simple truth of the matter is that in MMOs, choice and options are a lie and illusion. It's simply better to have a job designed for a specific role and leave it at that.