When it comes to cooldowns you need rather good math to figure it out, but until I get something solid on the matter I'm gonna keep doing what I doing which is:
Shout/prepot > Charge > rend > CS > DC/MS > OP > Slam > MS, etc with Heroic Strikes thrown in real often. Once DC ends you make sure you got Colossus Smash (I don't re-use it during Deadly Calm, I save it for the recklessness): CS > Reck/MS > Slamslam > MS > (hopefully new CS) > Slam > MS > Slamslam.
That's influenced by the fact that I got Heart of Rage. It will proc during the Deadly Calm and if it doesn't; fuck it. I delay Reck until it does even if it means having no Golemblood (Heart of Rage is alot more strength than Golemblood, but also influenced by fight duration).