Alright so I was really bored today and went into ToC25. We were at Twins when I accidentally dosed off and hit skull bash too early on the shield cooldown thing...but it interupted it. Shocked I tried it again on the other boss when she did it and viola bug found and confirmed.
Skull bash can be used to interrupt the twins cast while the shield is present. Not that big of a deal now, but if some guilds want to go back and get some cool achievements before cataclysm this should make it a lot easier. Enjoy and always report any other bugs found with it so we can fix it before the next patch.