Whirlwhind is one of the epic 1.0 spells; You *should* automatically be granted it at 90 or so, IIRC; It's *possible* you may have to do Epic Repercussions, though.
I run 2 zerks and didn't sound familiar. I don't see it on my spell list and not under Beserker tab in AAs, looking on EQU. Will check in game tonight.
It's most likely from not doing the quest to obtain it. Believe that's also why i do not have it. Especially, in my case, my newest alt is a boosted toon with very little older content done right now.