I'd suggest going with modified carnage tank spec (http://goo.gl/r9Tz9B). Dishes almost same dps as full carnage spec while having good survivality on offtanking stuff or surviving aggro (when you decide that soloplaying is bad idea in mmo). Just frenzy stuff and if tank needs help, just forced engage to ease his burden and if more is needed ->goad +irritate should be enough from offtank's part :P.