What if PW: S was a bit of a cooldown, completely changing the emphasis of the spell. I was first thinking it could apply to discipline in its entirety, but then thought of maybe implementing the concept as a pvp (read: "interesting" "choice" - the blues) talent for disc (or holy!!).
So the first concept is putting a decent cooldown on PW: S to make it a big deal, and maybe have a secondary benefit of granting something to the target. Currently, you have the "disc-nay-sayers" who want your typical disc priest to think of PW: S as a powerful instant danger heal instead of a filler to consume 9/10 GCDs; this would keep them happy. It would make everybody happy, I think, because it would make PW: S more interesting. Sure it would end up as a relatively low portion of your heals, but let's say PW: S being something like 20% of your total. Add DA in there and some crit/mastery gear, and you'll maybe have 10-15% of your total healing being DA. I think 45% of the total being absorbs still sounds pretty cool. Druids in cata might have a similar amount coming from HoTs!!
Two things come to mind immediately. One, you can make the bubble big enough to really put a dent in big incoming damage. Two, Weakened Soul will likely have less than 99.99% uptime in an environment like this.
Another thing comes to mind, which is that it will mean disc priests will not always pre-bubble (I think currently in 5v5 for example, prebubbling entire team means those plate dps with 35k in their arena gear have more like 43k. Or those clothies will have 35k instead of 28k. It's pretty dramatic (until it gets stripped away instantly by loldispelspam ofc).
As a "stealth-nerf" it would also means mortal strike is more effective against disc priests (atm since bubbles are such an integral part of disc priest defenses and they ignore ms...).
The secondary effect I was really thinking about was making PW: S make you immune to snares or something while it's up. This could be the disc (or holy!) pvp talent I was thinking about before. Honestly, the idea hit me when I was thinking of that arms warrior knockdown, and thinking how gay it will be if it's considered a knockdown (and not share any drs because its unique).
Warrior: LOLKNOCKDOWN ORLY?
Priest: LOLPW: S (immune) YARLY.
Warrior: :'(