This mentality is kinda funny since that's literally what we do with dps CDs.
That said, I think invulns are fine. I would be much more interested in gameplay that was designed around "TANKING" rotations. As in, the damage coming in was not survivable on a constant basis without proper play, not JUST the occasional tank buster.
They could give us longer tank CDs (30s), more of them, etc.
Eddit - And to add to this, I think invulns provide a unique opportunity for gameplay that should remain.