Dispersion isn't new idea, it is only remake of iceblock, divine protection ..... I think shadow priest need something new.
My idea is:
Focus to Shadow Soul:
(10sec -30sec cd)
When activate, you can cast your next shadow spell on you or on your party member and this spell gains a new effect:
VT - regenerate mana
SW:P - something like renew
mb - heal the target
Vamp. embrance (can cast only on party member) - may something like Soul link
SWD - you gain dmg from it, but next attack on you stun the attacker for XXsec
mindfly(become instant cast) and increase your run speed for XXsec
well dispersion is a watered down version of those, only because iceblock u are completely immune, 0 damage received. Divine protection you can still cast heals or offensive spells and Divine Shield well immune until someone mass dispells it like on iceblock. dispersion lets us run around but thats about it... my experience with dispersion has been bad so far. Everytime I use it, I die within seconds of it coming off. I am praying that they either alter it, or just scrap it all together.