Need some DK tanking tips

[:1]Hey group.

So I was recently pugging a FL group, we downed Shannox after the mage finally realized he shouldn't be slowing the the dog until after he picks up the spear......

But anyway, after the kill I had their raid leader whisper me saying my avoidance is crap and I need to stop gemming for stamina.

Idk, I mirrored the gems of some of the top dk tanks on the server so I thought I was doing it right. If you could, please check my stuff and give me any suggestions I could make.

Also, I'm not sure I understand the new tiers 2 piece bonus. It says burning blood causes your attacks to act like there are 2 diseases present on the target. Does this mean 2 additional diseases? Cause if not, shouldn't we always have 2 diseases up anyway...?

And one last thing. I've heard a lot of bad things about DK tanks for Firelands. Generally, things along the lines of it doesn't matter how much mastery you have if you get 2 hit. Is it true that by lacking a shield we're being gibbed since we are getting so hard? I really didn't seem to have much of a problem, the disc priest on me only had to heal 9k hps to keep me up, but are other bosses harder? If this is true, should i start getting rid of my mastery for more avoidance?

Thanks for all your help.
firstly: enchant your gear

and to the gemming fiasco, the higher end DKs can get away with gemming stam because their gear gives them good enough mitigation/avoidance without gems, so you should probably go with a mastery build.

the 2 set makes your melee attacks cause the target to have a debuff called 'burning blood' which does 600dmg per 2 seconds if its up.
the disease part means that even if you dont have diseases up, your attacks will act like they do. i.e. some attacks do extra damage if theres diseases up, if you have none up and you have the 2 set bonus, they'll do the same damage as if there were diseases up.

and in heroic 25 man raids, DKs are pretty much trash
heroic 10 mans we are still pretty bad
25/10 mans we arn't too bad, but paladins/warriors/druids are still better imo
never gem for pure stam, if you want more health, go with +20 mastery/parry + 30 stam.

for the 2 piece, if you're doing 10m and you're the only one who can apply frost fever, then you need to always keep those up.
The top tanks are worried about doing heroics thus they gear for heroics.

Read the tank sticky.

Check out askmrrobot.

None of the bosses are hard in 10m, it's basically all on DPS and heals. In 25m and heroic modes you'll notice the DK squishiness.

I see nothing wrong with your current avoidance, you seem to be going for mastery and avoidance, I prefer to choose one or the other.

You should definitely pick up some better trinkets and enchant your gear.
The 2p does essentially nothing but a 400 DPS increase. It doesn't place the necessary tank debuffs up for you, so you still have to put diseases up.