Source for some of them.
The rest can be found looking over the new talent calculator, namely blood of the north and endless winter/chillblains.
Here they are, for the most part:
-- The ghoul is doing too much damage. He is receiving 100% of death knight strength, which is much higher than most pets.
-- Chains of Ice is going back to be being dispellable. It is probably the best snare in the game at the moment, for a class that already has Death Grip.
-- The same is true of both Strangulate and Mind Freeze. Strangulate's cooldown is going to go up. Mind Freeze remains the quick interrupt.
-- We're increasing the cooldown on Anti-Magic Shell. We don't think this will hurt DKs in PvE much, and it still leaves you with Icebound Fortitude to use often.
What GC forgot to mention was this:
Chillblains and endless winter have swapped places. Remember this thread? (maybe, maybe not. :)
Blood of the north has been updated (or will be soon) to make blood strike more attractive. Derived from here. (which is also why you see pestilence on botn as well, now)
In addition, I know we at least have this to look forward to as well.
Death Coil's coefficient was increased. We more recently changed the base points, say from 390 to 440 at rank 5. You probably don't have this last change yet. If you used a Death Coil every rotation, that's a lot of extra damage.
And, don't forget this, either!
We found that the real problem, IMO, was Death Coil and Frost Strike weren't hitting hard enough relative to other DK abilities, so they didn't feel like they were worth the button push, and subsequently, building up runic power didn't feel like a big deal. Both Death Coil and Frost Strike received serious buffs.
All in all, these are steps in the right direction.