Funny you should ask, I just suggested this spec to our offtank:
http://www.wowhead.com/?talent=TZVxzVRxoVzZ0EtoGMz0x
Flurry + 1hspec combine fairly well for dpsing and when offtanking provides enough agro. When attempting to stay at #2 agro, the improved rage gen and agro from the 2 talents helps make up for not having shield slam. If you use tank gear with agility on it, the agro ramps up even better without hurting your mitigation too horribly.
The big downside is no imp tclap but you can't have it all.