I've been a Frost Tank for quite a while now, but after leaving the game for 4 months, I've come on here to look for a bit of advice. However, it appears that nothing has really changed for DK tanks since patch 3.3.
Your main issue for me is your 2x1H's get a real weapon. DW was good for ulduar, from memory. But I know it was nerfed in either 3.2 or 3.3 and hasn't been great since.
As frost, your threat build should be as good, if not better, than better geared tanks. However, your spec looks way off. Frost doesn't have the survivability that blood does, but you miss Frigid Dreadplate out of your spec....why??
Personally I struggle to keep my defense rating down...... the theory being, the more over the cap you are the more heavily stacked on defense items you are, the less stacked you are on avoidance....
I'm looking for a way to increase my dps, without sacrificing survivability..... but I'm not sure it's possible. I can only do about 2k dps, but I never get over-agro'd single target as frost anyway, but the added dps is always useful in raids. In blood I really struggle with agro
Just so you know, glyph of dark command will be coming off, and replaced with death + decay, only just got to the hit cap
I'll have a think and see if there's anything else I can think of over the next couple of days.
Edit: You also have the wrong enchants on weapons imo, try the 1H Defence + 1% stamina enchant from Runeforging.