Your expertise is way too low. Try getting that up around 25 to push dodge off the table, that'll increase your DPS by a couple hundred. As a DK tank you definitely should be doing more than 1k DPS, I can't speak to your spec or most of your gear, but get rid of your Block Value pieces as those are wasted itemization for you.
Your armory talents are different than the ones you posted. But I'll go by your blood one.
I would suggest you use heart strike in your group rotation too. Back when I was still blood spec I used this rotation:
IT-PS-OB-HS-HS-OB-HS-HS-HS-HS-HS-HS -repeat, and also work in Death Coil when you're waiting on a rune to recycle or runic power is maxed.
As for groups, I'd probably go with:
DnD-IT-PS-Pesti-OB-HS-HS-OB and then repeat.
The problem with blood is that blood boil does very very poor damage right now. Generating alot of threat vs more than 2 targets will be alot harder for you than anything short of maybe a druid and alot of prot wars.
Oh and if you're wondering about the 6 HS in a row, that's because after the two Obliterates, you should have 2 blood runes and 4 death runes up. With that rotation, vs a boss you should do very good dps and a ton of threat. And don't forget if it's only two mobs HS will hit both of them since it's a cleave now.