I don't use the armory, but use Wizard's wardrobe. As a magplar, I queue as a DD, but have tank and heal offsets saved. I mostly don't need them, but I prefer to have and not need than to suffer through ping-pong mobs and 'healers with bows'.
Oh, I also votekick the fake roles out just before the end boss too(assuming they don't even try to do tank/heal - if you are 16k with a shield and taunt then that is fine).
In vet there are consequences.
Fake tank in many cases means he will die from 1-shot many times, and will have to kite and roll dodge a lot.
Fake healer means group will have no heals. Tank can usually survive, but DDs may die many times.