One of my biggest pet peeves in MMO's, Rift especially, is when I'm forming a group and a warrior/cleric joins and refuses to do anything but dps. In Rift it is so easy to get a second role and fill it with a tank or healer soul I don't understand why you would deny yourself the ability to get into any group.
Now you may be thinking, "Well rogues have a tank soul and mages have a healer soul, shouldn't you be saying the same thing to them." Well yes and no, it would be smart, but I don't hold rogues and mages to the same standard because only one of their eight souls can tank/heal, but pretty much half of warriors and clerics souls can tank or heal, so it's hard for them not to make one of their souls a tank or healer. And, for the record, I have a rogue with a Riftstalker role and a mage with a Chloromancer role.
Sorry if this post sounds standoffish, it isn't meant to be mean, I just think people should know.