Replace Glyph of Stoneskin with Enduring Healing Sphere. These are pretty much indispensible on most fights where you tank a boss in one position for an extended period of time. You can strafe to one side or the other for emergency healing, like having an extra healing potion or two.
Since we pull threat so easily from other tanks, I've also gone for a bit more mastery. It comes in especially handy on Horridon. I'm 530 ilvl and I sit at hard cap expertise, hit cap, 5000 haste, 40% raid buffed crit, and 18% raid buffed mastery. It really does make a difference.
People will say you don't "need" any extra mastery, which is true. But it can certainly help, and you don't give up a whole lot to get it. I can take 6-7 Punctures on H Horridon without need of cooldowns if I have to.
As others have mentioned: You need to be keeping Shuffle up. A number of people have Weakaura strings you can download for tracking the amount of damage staggered, etc. You should be using Keg Smash on CD, and saving Guard to use just before major hits like Triple Puncture. Use Dampen Harm when you're at like 4-5 stacks of Puncture. You should also be ready to use Expel Harm and Chi Wave right after taking triple puncture. And remember that under 35% health, Expel Harm has no CD, so you can spam it in emergencies if needed. Be quick on Purifying on Triple Puncture as well if it takes you into red stagger.
We're pretty much the most durable and long-lived tank in the game for physical damage fights with large telegraphed hits like Horridon. Definitely not Paper Tigers. Your damage needs to go up a ton as well. I see on Ji-kun normal you did 77kdps. You should be able to manage closer to 120-130k. BrM DPS is incredibly high, and should easily smoke DK tanks by 60-100%
Compare N Dark Animus between your log and mine (with me at that point like 526 ilvl) -- 114k vs 67kdps
http://www.worldoflogs.com/reports/o...?s=2973&e=3204
Also: Use Armor and Mastery Elixirs instead of Stamina flasks. An extra 15k health or whatever is rather irrelevant. While the Elixirs will give you effectively 3% more mitigation.