unless I'm missing something the castrandom part shouldnt work at all because each time yer cast something from the castsequence and incurring a gcd

You should shorten yer castsequence, only thing that might make it thru an entire castsequence is a boss and I'm not even sure of that :P

What might help is if yeh change yer castsequence not to reset on target/combat but on time depending on yer longest cooldown spell

like
reset=30 Vampiric Embrace,Devouring Plague, Shadow Word: Pain, Vampiric
Touch,Mind Blast, Mind Flay, Mind Flay, Mind Flay, Mind Flay,Shadow Word: Death

(probably could use some more tweaking for timing) yeh can do something similar for the warlock

would be a good idea to put Curse of the Elements on a separate button

yeh really dont need to put fade into castsequence its only temporary aggro dump