Your ub health is low, I'm guessing it's in the 21k-22k range in Frost Presence. I actually started tanking heroics on my dk w/ 22.5k ub hp (in FP), and that was the bare minimum possible and required a good, well-geared healer. I remember tanking H CoS for the first time with similar stats as yours, and on Mal'Ganis the healer had to chain cast his biggest heals the whole time.
What I did at that point was to focus on getting the all the epic and BiS items from Cider's Easy 540 Defense Guide. That requires grinding Hodir, Wyrmrest, Ebon Blade, and Argent Crusade rep, and getting several crafted items: Titansteel Destroyer, Tempered Titansteel Helm, Tempered Titansteel Treads, Titanium Earthguard Chain, and Titanium Earthguard Band.
For Hodir, farming and buying Relics of Ulduar helps alot. For the others, run alot of instances wearing their tabbard, including all the Heroics you can currently do, and you'll have Exalted in just a few weeks at worst. The grind looks daunting, but it goes by fast if you focus on getting it done. If you can, run HoL and HoS reg and heroic, since they drop Relics and you wear tabbards in there.
That requires a bit of grinding, of both rep and gold, but should get you to the point where you can tank heroics comfortably without straining healers too much.
At least you have two gathering profs, which should make the gold grind really easy (especially w/ On a Pale Horse in your offspec/daily/farming build). I strongly advise not dropping one and leveling a crafting profession until you have all the gold you need to buy crafted tanking items from Cider's list.
Edit: Experiment w/ different specs too. I also prefer Frost for tanking Heroics, but prefer this 15/51/5 spec.
The 5th point in Killing Machine only makes a marginal difference over the 4th point, can get a way without it.
Bladed Armor gives around +700AP in Frost Presence, which buffs your strikes, spells, diseaeses and white dmg, hence Bladed Armor > everything in the 2nd tier UH tree.
3/3 Scent of Blood lets me spam both Rune Strike (macro'd to most keys) and Frost Strike nearly continuously, and 2H Weapon Spec is another threat buff.
You shouldn't need 2/2 Runic Power Mastery since you should be spamming Frost Strike (and Rune Strike should be macro'd to other abilities so that it is spamming when it's up too). If you're consistently filling your RP bar, you're doing something wrong.
As long as you've glyphed Howling Blast, you don't need Epidemic. Diseases last 15 seconds without Epidemic, and HB will refresh them every 8s (quicker with Rime procs). In Heroics, a single DnD + HB + BB is enought to give you an insurmountable AoE threat lead, so you don't need Morbidity either.
And if you're using both Dark Command (8s cd) and Death Grip to pull runners (which never happen if you have BA, SoB, 2H, and glyphed HB), you don't need a decreased DG cd from Unholy Command either.
Glyph of Icebound Fortitude is only for PvP. A tank w/ 540+ defense cap will already have ~35% dmg reduction on IBF, so that glyph is worthless for tanking.
With 3/3 Scent of Blood and 2/2 Chill of the Grave, you don't need extra RP from Glyph of Icy Touch, and can replace it with glyphy of HB or something else. I prefer Glyph of Oblit (+20% dmg on my primary strike besides FS), and Glyph of UA (UA is a little weak, prefer to buff it, especially with upcoming patch 3.2 increasing the cd on IBF from 1m to 2m).