I Haven't seen an Xbox one mod 12.5 PvP feedback thread yet so I'm making one. Here are my 2 cents regarding the new PvP changes. Feel free to add, agree, disagree with whatever:
1. TRs continue to be the class with the most burst damage (unavoidable) with shadow of demise, control, survivability and cc in PvP. The "Recovery" (30k plus recovery stat) or "perma cb" rogue can still drop smokebombs back to back while spamming encounter powers/dailies and controlling an entire node, while still being able to kill relatively fast. Also regarding smokebomb, having it add 1 stack per use means you will almost never become immune from one TR doing this. As a result smokebomb is and will continue to be the most overpowered cc effect in the game.
2. CC diminishing returns does not seem very uniform. Some control effects from items, enchants and boons do not seem to add stacks (thunderhead, curse ring, impenetrable jungle, etc), while others seem to add them too fast ( wizard control powers, trappers, etc). This either results in being CC immune really fast, or stunned for a solid 30 seconds unable to use a power. Initial CC is very strong which is fine, but imo system should be ironed out a little further.
3. Old school mod 5 feel returns with healing suppression and armor penetration suppression increases. Now you actually have to watch your health, use powers actively to survive, and make tactical retreats when needed. Overall a great job in this regard. Also removal of tenacity is a huge step forward in bringing new players to PvP.
4. Permanent solo q is great as well despite issues with players not playing and matchmaking issues with team balance. I'm not sure if anything can be done to fix this though because of low pvp player population.
5. Regarding solo q, certain classes are really strong when stacked on one side of a team, while others seem less so (not taking into account player skill). TRs, GFs, and OPs are tough to kill and can make a match lopsided when there are two on the same team. GWFs, SWs, CWs, and HRs have the opposite effect. DCs are kind of in the middle depending on what build they are (DPS or healing).
Overall though significantly better than last mod in regards to progress.