You've currently got a decent gear set so if you're concerned about surviving in heroics, you need to find new healers.
As for your proposed spec, the math favors the deep wounds in the 15/5/51 or 15/3/53 build over 5/5 cruelty. The ability to leave bleed debuffs on mobs shouldn't be overlooked. Speccing into revenge is useful in heroics as you can stun/interrupt with it on most trash.
Parry and expertise are apples and oranges - expertise is a threat stat and ideally you'll want to have at least an expertise rating of 26 which will stop enemies from dodging your attacks. Parry on the other hand is an avoidance stat and slightly less attractive than dodge. So to answer your question, they are both important for different reasons. On fights when you need to pump the threat out, you'll want expertise while on content where you're more concerned about staying upright and mobile, avoidance stats would be preferred. If you're mostly running heroics, I'd lean towards the expertise side of the equation though.
Not sure if Armory is broken but you have no trinkets? Consider changing your glove enchant to Armsman instead of +18 stamina. Also, changing your chest enchant to +22 defense would let you swap those defense gems out.