Hi,
I have only looked through your logs from 02 October, and I noticed something, that I find a big issue in your tanking, which is Shuffle uptime. It keeps falling off all the time, which should like never happen. In the most cases you kept it up only 50-60% of the time, which is very very way too low. No Shuffle makes you pretty much vulnerable, which you don't want to happen as a tank.
Correct me if I'm wrong, maybe its always up when you're on the boss and it just instantly drops after you swap off, but honestly this doesn't seem legit to me.
Shuffle helps a lot on Iron Juggernauts mines tho, so...
About your gearing
First off, I tank in 10-mans, so my opinion is just some theory, but if it doesn't make any sense, feel free to correct/critique it!
1.) Your hit/expertise aren't capped. Loss of Chi imo, they SHOULD be capped on your ilvl.
2.) If I was you, I'd only go for Stamina on Enchants, but not on gems. Besides, I don't see the point of Agi+Stamina gems in Red sockets. In case you're trying to go for damage smoothing, you should gem for Mastery, not Stamina. Put in some Agi+Mastery or Exp/Mastery gems!
3.) Way too low Haste. Just way too low, and I'm guessing thats why your Shuffle always drops. You take so much damage, your Stagger goes red, you panic and keep Purifying. That means you are out of Chi in no time, your Shuffle drops, you start taking even more serious damage, you try to Purify harder... Its not working. :P What you need is a steady high Mastery + Haste rating.
4.) Purifying. You rarely hit Heavy Stagger, that means you're clearing Yellowes, maybe even Greens. Don't. "You should be always in red", and only clear over 100-150% Stagger'd damage.
Well, yeah, those were my first thoughts, I'm not the best at log reading, but yeah. Hopefully it will help you getting better.
Cheers,
Adam