At the moment it’s a mix of things that promotes the current meta. If tanks survival wasn’t a limiting factor we’d see mw monk instead of disc priest for example, or if groups survival wasn’t the limiting factor we’d see 4 DPS and 1 tank.
It’s healthy to be limited by several things, not just one.
Buy yes, you’ll have to wait longer in queue as an off-meta spec due to people preferring meta-specs even when they’re not needed.