This I have to disagree with. STO (and CO to an extent) are unbalanced in favor of DPS, but more traditional WoW derivatives have much more viable roles for the other 2 sides of the trinity (healer/tank).
In fact The Old Republic is suffering a bit right now because BioWare made the mistake of giving the cool dual-saber/dual-wield abilities to DPS classes (Marauder/Sentinel/Assassin/Consular). As a result a ton of nerdy free-to-players flooded the servers with DPS. It's not unusual to find a small guild full of Marauders ONLY.
And the way Flashpoints are constructed most are very difficult if not impossible to finish without a proper tank. I have nightmares about wiping 25 times in a row trying to finish hammer station with 2 marauders and a mercenary (the bounty hunter class that's DPS-centric).
For the record, I'm an operative with healing spec, and almost never have trouble finding a group.