Brage, most people take Shield Spec because it is simply overpowered. It's basically infinite Rage when you use Shield Block and is the largest source of Rage through talents by a massive amount. It makes Heroic Strike and Inner Rage very easy to use.
(To be fair, I've argued on the beta forums that it is too strong, but GC had replied that he doesn't see why people view it as a semi-required talent. Unless they somewhat nerf it, I don't see many other talents being as strong. Battle Trance gives much less Rage per point, for instance, Shield Spec is controllable via Shield Block, and its power scales with our Mastery.)
About Thunderstruck, it's hard to get a feel for it. I'm not convinced that Warriors will actually be the ones keeping up Thunder Clap on bosses--as our version of the debuff is easily tied to the lowest TPS and highest opportunity cost of applying it.
In a single-target rotation, the biggest issue with the buff is that it only lasts 20 seconds. Thunder Clap lasts 30 seconds. So in order to get the Shockwave boost on a single target, you have to use Thunder Clap considerably more often, which probably negates any TPS boost from the Shockwave portion. So, sadly, I don't really see this being a single-target thing to do.
So, not sure I will pick up the talent or not. Perhaps if the passive bonus was a little stronger. 6% is a bit low. The only upshot is that if you get both AoE talents, Thunderstruck will boost the value of Blood and Thunder due to the Rend increase--however, I really don't like spending that many points on AoE talents unless we find out it is really needed.