Drop some hit and expertise since they are over the cap. Drop your Icewalker on boots for the attack power enchant. I don't know why you have your Nightmare Tear in your helm since the bonus is only +8 crit. You could've put it in your boots for at least +6 strength bonus. Also why do you have a blue gem that's agi/stam in the red socket on your shoulders? You're wearing tank shoulders which don't help your dps aside from the strength. If you're going to take Frost as your sub spec then you need to drop Reaping. A Reaping build is used with Unholy/Blood. You should also have 5/5 Necrosis.
For Unholy the T10 4pc is very good so I would go for that first. An upgrade for Mirror of Truth would be the Needle Encrusted Scorpion from heroic Forge of Souls. For a couple thousand gold you can buy the Darkmoon Card Greatness also.
Do you mean you have 2 additional points? You should also have 2/2 Dirge which I forgot to mention in my previous post. If you enjoy the Reaping rotation you can keep it but it means using Blood instead of Frost as your sub spec. The Elitist Jerks Unholy thread is a bit vague in the guide itself as to when exactly you should use each spec variation. Blood sub spec without Reaping is for lower gear levels. For someone with 2pc T10 you can either go Frost sub spec without Reaping, or Blood with Reaping. I would read some of the posts over there for more detailed information but if you have a proc weapon like Bryntroll or Shadowmourne Frost should boost the number of procs from the added haste. Icy Talons also affects stat weights since the benefit of haste increases.
I'm not a DK, I don't play a DK, and I honestly don't know much about DKs, so I can't really help you in a direct manner. However, I'd like to try to help indirectly. I found this and gave it to my guild's main DK and he said it helped him a lot. So I'll pass it on here as well.