Have a warrior alt, thinking of leveling as prot.

[Sir_Die_alot]

That being said, tanking and soloing as Protection are somewhat different. Not by a great amount, as you're using the same abilities, but there's still a difference. While tanking, you want a fast weapon to maximize your Heroic Strikes, as that gives more damage than the difference in damage from Devastate would be with a slower weapon. While soloing, you won't have enough rage to do that, so you'll want a slow weapon to maximize Devastates.

I'm not sure when it happened or if it's just always been like this and the trend is changing but using a slow 1 hander for tanking seems to be taking off. I know the MT in my guild switched to a slow dps 1 hander and I can go full out 10kish dps with my fury warrior and not even get 40% of his threat. He also has a top 10 prot dps ranking in nearly every fight in 10 and 25 man ICC.