I'm a fan of having multiple classes able to fill a role (such as being able to invite either a paladin or warrior to tank) and also a fan of classes being able to fill multiple roles (such as a warrior being able to tank or melee DPS).

I agree there should be another healer option. Perhaps that aspect of BRD could be buffed, with additional songs that help it fill a mainhealer role. Another possibility is making it so PLD could have a mainhealer mode, similar to how WAR has tank and DD modes. Of course, a new class that could mainheal is always an option too.

In addition, I wouldn't mind if they buffed MNK so it could tank better.

As for the viability of classes/roles, I mainly play my DRG and don't have any trouble finding a place in groups. People aren't beating down my inn room door demanding I join, like they would with a WHM, but its not like I'm some leper/pariah, as some people claim all non-WAR/WHM/BLMs are treated.