The issue with PW:S now is that it's going to scale far better than the other heals due to its practically non-existant overhealing. As it stands, the average PW:S now shields for an average of 180k (probably close to 200k now with top-end gear). For reference, this does almost as much HPS as a PoH that hits 4 people, but factor in the fact that your PoH will always have higher overhealing, and the balance in power shifts towards PW:S under almost every situation. Even under ideal conditions for PoH (heavy raid damage when the raid is stacked), there still will be non-trivial overhealing for PoH due to all snipe healing from raid wide smart heals, and you would be better served by using a PW:S->PoH rotation to take advantage of BT.
Anyway, the problem isn't only with PW:S numbers, but also to do with the fact that the effort vs reward ratio is off when it comes to PW:S. It's an instant cast which means that it isn't susceptible to heavy movement (Winds on P3 H-Lei Shen, Durumu's Maze, DA Fonts to name a few), has great spot healing capabilities unlike group/raid wide AoE heals, and all this while still pulling great numbers. This isn't even including the fact that it serves as a great alternative tool, when SS is down, to mitigate burst mechanics. The main downside to PW:S is that it can be slightly inefficient, but the introduction of gear upgrades/LMG has made it very mana sustainable.