I know we have a few Tank DKs so I figured I'd pass this info on about T10.
The set bonus for T10 is a +20% DnD damage bonus so it has potential to be used in a single target situation now especially if you glyph for DnD.
The general conclusion was that even if you glyph for it, it's not much better than using your normal single target abilities (i.e. HS+DS, BS+OB, BS+SS). The issue is you're generating less RP typically and with the exception of Unholy, the threat differential is not large enough to warrant any changes. Additionally, you lose half your runes each application of DnD which loses a lot of flexibility.
Personally, I'll be sticking with my normal rotation; plus I don't think I'll be nabbing my second T10 piece for quite some time since I want to get the Trinket and Belt or Cloak first.
Here's the TankSpot forum that broke down the math for this:
http://www.tankspot.com/forums/f14/60096-dnd-t10-glyph.html