I thought a lot about your official post and also about Kaesebrezens statement about shadows limited mechanics. Now some things became clear to me, because I recognized a pattern.
If you want to understand the (PvE) balancing problems you have to be aware you have to include and consider three cases
1) shadow on its own
2) shadow with mates controlling the battlefield
3) PvE damage
If you look at 1). SPs are definitely underpowered. Just look at 1:1 situation, where most classes hinder SP of doing anything or 2:2 with mates without heavy cc.
SP clearly have to high damage potential, with too much utility. But this does not weigh in such situations. It is simply countered by cc. To understand what I mean, just play 1:1 against Frost, Warrior or Rogue or..... or 2:2 with a Resto. You are helpless against so many combs, because you cannot do anything useful if your under fire of a cc heavy class.
Th e noticeable fact here is: This situation cannot be balanced! Why?
If you remove CC of others or if you give SP more cc or defenses, SP becomes to strong, because of its potential. If you give even more damage or utility to SP it helps nothing, because it is still countered by cc.
Shadow is too strong here. We all know. And the best about it: It is pretty easy to balance by reducing burst damage.
The "downside": A) It just makes situation 1) even worse and nobody cares and B) It effects PvE damage, where we have a problem for month now.
3) PvE damage. And now the "limitited mechanics" comes into play. Let me extend that thought. It is not only the limited mechanics. It is the fact in PvP cc and burst/utility are tried to be balanced against each other.
No matter how you try to fix the PvE damage problems, there will always be concerns from fraction 2). That became clear to me, while reading that 10% to PI are to powerful in PvP. I mean a cd where you have to stand and cast....MF.
Therefore I do not even think buffing PW:I would help (as you suggested). because even that would hurt situation 2).
The fact is:
More PvE damage hurts Situation 2). No matter where it comes from. when a Shadow can act unhindered in PvP it is to strong. To give more damage to it makes it even stronger.
That is the trap we are caught in from my point of view. The reason is the limited shadow mechanics and the cc against damage balance in pvp. It just failed and we are at the short end. Why?
Because all efforts are dedicated to case 2).
The statement by Blizz "SPs are clearly OP in PvP and need a nerf" does show this. Shadowpriests also does have a significant single target and scaling problem. But it was never mentioned that clearly and all action so far had is main focus on fixing 2). (To call this "flying under the radar" is a bit cynical.)
This does not say the first statement is not correct. It is. But the second is either.And only one of the issues can be solved without hurting the other.
After this thoughts I am pretty disheartened about PvE 5.2. I do not know, how you guys think about it.
As I cannot post in official US forum, feel free to take any passages from my post to copy/use them as you like, if you think it helps our issue.
Thanks and regards