Bad logic is most certainly bad. The hybrid tax has nothing to do with raiding or what utility is brought to raiding, and does not affect how people are chosen to form raids.
This is a false statement and you know it. There is power in being a hybrid.
For example, just last night I was running a heroic CoS with a pug in LFD on my shadowpriest. The healer (a pally) was in pretty weak gear but the tank was a "gung-ho I ain't stoppin' for nobody" type. He rushed on ahead without even looking back.
Twice in that 10 minute instance, he almost died. I mean - under 5% health. As a shadowpriest, I saved his life and the group by shielding and going heals. After he was caught back up, the flailing healer caught her breath and we continued on. Even while healing the tank, I still had 4~5k dps on the meters. I was back in shadow and melting faces before combat ended.
My mage and hunter would have been struggling to hit invis or feign death in those circumstances - it would have most certainly been a wipe had I not been playing a hybrid to maximum capacity. I was filling a ranged dps slot (same slot that a mage and hunter would fill). I was worth at least 200% more to that heroic group as a shadowpriest than a pure class.
Now in raids, this utility is minimized greatly - but it is still present. It's still entirely possible that a raid may call on their shadowpriests, elemental shamans and boomkins to step up healing in a close-call situation. It may be even more of a realization now that healer mana in Cataclysm requires management and isn't faceroll, like in Wrath.
You guys can downplay what it means to be a hybrid all you want - the fact remains, a hybrid character will always have more potential value to the player than a pure class - regardless of whether the player recognizes it or not.