i set DS on Meta and Boss, because without Meta our DS piece of ....
you don't understand me.. i'll try to explain: we begin the fight. we need accumulate around 900 rage for using Meta + DS + Imp of Swarm. But we can't do this (mb with lowhaste and without t15), because we always have molten core procs from Hand of Guldan and our imps (yes, imp of swarm isn't cooldown, so they can proc). CR use Meta (rage), touch of chaos for corruption update and damage (rage) and 1-2 molten core procs (80 rage each). i damage dummy around 20 minutes. and i can't ger more when 500 rage because CR always waste rage for molten core procs. you need condition.. something like "check DS cooldown (2 minutes or 80 sec with 4t14), if cooldown more whan 30 sec then use molten core procs (not always in meta because it's +30 rage), if less whan 30 sec then we need 900+ rage then DS + Imp of Swarm + Doom if needed + touch of chaos if needed + molten core procs".
i think what your char have many haste rating so you can accumulate 900 rage with your conditions. But me (and many others) don't have rppm trinkets so we don't need many haste, crit priority. and we can't assume 900+ rage and can't use DS and Imp of Swarm with full rage. instead these CD waste of dps