Yes you're right. I was thinking of the paladin rolling on it, off-spec isn't the word, more like if it isn't really the right item for them but BiS for you
Warriors on the other hand are in a more difficult position than most, same with classes that can heal. People want dungeons so they desperately need tanks but most raiding warriors just want the dps stuff now so they can switch arms or pvp.
It would be prudent to let the group know first, maybe he did, but I suspect even the OP would still have run the dungeon in either case.