I did a few runs with a significantly easier rotation, basically scrapping DnD and using OB and HB (in that order) whenever I had the runes for it (not even bothering to look for unholy runes to cast OB). This rotation means you don't have to watch your runes at all. It ended up at 121523 dps, a loss of less than 0.3%. Even though the more complex rotation sims higher I'd say that not having to watch your runes at all in a raid encounter would at least increase my performance more than that.
I know this is a theorycrafting discussion, but I think it's worth pointing out.
Here is the rotation I used if someone is interested (using PL and BT):
So this would basically be the 2H priority except one would cast HB with Death/Frost runes instead of waiting for another rune to come off CD and allow Obliterate? Did you check scale factors for this priority? Does it still favor mastery over haste?