Well i just recently became hit capped and I am trying to improve my gear but I am stuck because the gear I have seems to be the best gear I am able to realistically get. I will be tanking 10 man Naxx as Unholy Death Knight, but I want to see if there is anyway of improving my gear.
Go to wowarmory.com and search forBėllum, Level 80 Deathknight-Eclipse Complex- Gorgonnash
I checked your armory but you may not be in all your tanking gear because I don't see you as hit capped or crit immune. Since you stated you want to tank getting your Defense to 540 is your first priority. If your not crit immune it will be hard for healers to keep you alive through damage spikes.
Look to enchants and a belt buckle + Def Gem combo to help boost your defence right away.
If your worried about threat all I can say is I only have 148 hit rating and I have little problem holding singles or groups against some serious dps in heroic Naxx.