ok, as we are now out of Ulduar and moving into ICC, I've respecced from my Frost tank spec back to Blood tank, with a couple of tweaks to what I had before. Initial tests with training dummies are very favourable and the rotation is solid with good aoe threat as well as fantastic single target threat.
One thing I have lost is the Ice Block ability so faction champs will not have the initial freeze on pull, but that shouldn't be too much of a problem :)