Roles for Samurai, Red Mage, Dancer

[aesteval]

That indicates that there probably aren't enough people playing Tanks and Healers, at least in Duty Finder.

In DF is the big qualifier. Holy crap the sheer number of tanks I see roaming the open world. Joining a hunt party comes with a fair chance at the party being 50 - 75% tanks. Sometimes healers are still scarce in the open world, but they also have times in which they show up in large groups.