I am incredulous that blizzard is seeing 'very little of [PW:S] on live.' I use it on the tanks every time WS wears off in EVERY encounter, mixed with SS/PoH the raid. I will even PW:S and SS/flash heal JUST TANKS in fights like Lei Shi! The raid leader will ask me to PW:S strike targets on H-windlord, and I use PW:S during tornado phase on bladelord on any player who is dipping lower/not getting heals, as well as on windstrike targets. I'm sure I'm not the ONLY disc who does the same. Disc priests ARE using PW:S - dont give me that crap that they arent. I looked on WoL and browsed ranks of dpriests for heroic TOES, and each of them use PW:S a generous amount. I realize this is a narrow margin and not a good representation of all discs in the game - but it shows that discs who know how to get the MOST out of their toon use the spell.
Blizzards ceiling on mana pools forced many discs to stop using PW:S as liberally as they would have, because our mana pools arent the impressive force they were in DS, which could accommodate for more PW:S usage. By placing the mana cap - they limited which heals we could use - and we were forced to ask ourselves, which is the team going to benefit more from: an expensive ST heal, or a MUCH CHEAPER Aoe heal that collectively heals for more?
And for your comment to PW:S targets with lots of incoming damage...how ridiculous. You want me to PW:S 25/several players!? Are you serious? It would take me 1 second to shield a single toon for roughly 100k give or take a buff. Why do this when you can just PI/SS/PoH the raid/group in less than half the time for less than half the cost with a ceiling absorb of roughly 250k!? Which sounds more effective to you?