First of all, I really like the "hybridizing" as Unholy, I've done a similar thing with Unholy and Blood with 5 in toughness, up to veteran of the third war like you mentioned. Which is more of a throw survivability out the window and just hit the SOB spec (good for threat)
I like your build quite a bit due to frigid dreadplate. Which I never considerred when I made my current spec. As far as how you've talented it, it looks like the survivability is pretty solid. That Frigid Dreadplate is going to have a good synergy with Bone Shield's Uptime.
As far as scourge or obliterate. I have always found scourge stike to be a better choice for the two, considerring that it's damage is not negated by Armor of an opponent due to it being shadow damage. The difference won't be huge but it will be pretty evident without certain talents in the frost tree which really up Obliterate's damage.
Personally I'd stick with Scourge Strike, which will benefit greatly from 5 points in Black Ice. So I think as far as that is concerned, you may possibly see a pretty big difference in Damage.
If you're not benefitting greatly from Icy Talons, your other raiders will anyway, so as far as that talent is concerned, it was well spent.