1) Gems - Remove all Your stamina gems. Its not LK times any more. It`s just not. There is no boss that would hit You for 150k unless You are doing something wrong. All stamina gems is just fail in Cata. Red - Parry + Mastery; Blue - Mastery + Stamina. If You are going for Mastery then do it not for Mastery/Stamina. Avoidance is also important as there is moments when You cant refresh Your BS and Your only mitigation is avoidance. So Avoidance + Mastery until You get too much avoidance (which is far with Your gear) where Avoidance starts to pay on Mastery by avoiding hits and loosing incoming heal. You should not get stressed about that situation with You gear.
2) Talents - a bit strange but I guess its play style as most important talents You have.
3) Glyph - same as Talents - strange. It looks like You just love Your DnD and give all credits to it. By the way BB is real crap to generate threat. Its more situational and tanking only HC might be even worth it (if You dont break CC with it).
4) Reforge - everything seems to be OK. Main thing is to keep Dodge and Parry as close as possible. I think its up to You but usually (at least most I have seen/read) keep expertise at minimum 17. But I guess if You are not doing raids and not afraid to loose aggro on 25+k dps because of dodge,dodge,miss chain then it is OK.
With this all taking in mind You can survive and keep threat which is Tanks job. With this setup I can solo kill Sathiron (that's lame, I know), Lord Marrowgar (ICC first boss), trash pulls like in Lost City HC, ZG HC First boss etc..
If at first you don't succeed, you are running about average