I don't disagree with the changes - resto's needed the buff bad, and PW:S spam was far too powerful...but now, combined with the POH nerf last patch and the relative dearth of times for atonement, you've turned disc into a subpar healer that is brought for the external cd's ONLY.
Let's be honest - disc's heals are below those of other pure healers because of passive +healing bonuses that aren't present in the discipline tree. DA is supposed to make up for that, but only procs on crit heals (and the aforementioned nerfed POH), which hugely devalues mastery (+a %, on a % of the original heal only a fraction of the time is extremely weak). In addition, DA is a short duration shield that is unlikely to be consumed when raid healing (just ask the paladins how they like their mastery).
You've pigeon-holed disc into single tank healing with this nerf, and at that point I'd rather have just about any other healer for that job. Pallies have beacon, Shamans have the -10% physical in addition to very capable single target healing (now, with the buff), druids can roll a set of hots and take advantage of mastery, and holy priests - already a better raid healer than disc - get to go to single target chakra and crit far more than disc does while rolling hots. If I'm taking a disc healer to my raid (this includes myself - I'm headed back holy), it's because PW:B is needed for a specific boss mechanic, some sort of atonement cheese (no longer exists in the current tier), or there are huge MS debuffs (chim H, I'm speaking to you).
TL;DR: Give discipline something back in exchange for the large net nerf between 4.06 and this hotfix.
There's no way a Holy priest compares to a Disc Priest for single target healing. You are getting the same shield just a higher cost to it. This stops you from PW:S an entire 10 man raid pulling 21k HPS.