In July I wrote about why the developer idea that discipline priests would get 50% of their healing from shields was ridiculous.
This week Blizzard multiplied the strength of Power Word: Shield by more than three. Of course this didn't just mean three times as much shielding from shields, it meant casting more shields since Power Word: Shield became such a good spell with the change. It also meant stacking mastery over crit, further increasing the power of the shields. I now have one night of raiding data, and my total shields as a fraction of heals was 49.4%. Very near the 50% mark that the developers thought we might have.
So they were basically right, assuming you are willing to overlook the mistake of making our signature spell about 30% as good as it should be.