I would include WoD Subtlety in your list as well (and note that while Shadow Dance didn’t yet exist in TBC Subtlety, TBC Subtlety had a high skillcap for other reasons and you can go watch Neilyo duel vids to see why). But WoD is usually excluded for the combo points change. The only other real changes MoP -> WoD: pruned Shadow Blades (fine with this), pruned Dismantle (fine with this as well), pruned Redirect (discussed below), and pruned Shadow Walk (would have liked to see it stay since it was fun in Rogue v. Rogue matchups).
About the change to have combo points on the Rogue (and pruning Redirect), this was indeed a buff, but as for the mechanics of the spec it was more of a neutral change than many people realize… obviously you don’t have a need to use openers like Premed Garrote Slice target1, Cheap Recup target2, --> now you got your buffs up while peeling 2 targets, swap target3 and go (although nothing prevents it, it just isn’t necessarily optimal). But at the same time there is more reward and a larger space of use cases for using @focus or @arena1,2,3 macros for Cheap, Garrote, Rupture, Kidney, Gouge, etc and being able to interact more fluidly with multiple targets. So yes, it was a buff, but WoD Sub was still very fun to play and had technical and rewarding playstyle based around Find Weakness windows, managing many buffs/timers/finishers, and having disruption, burst windows, and hit & run tactics that all interact in fun ways with the core mechanics of the spec (energy/combo points and Find Weakness).
As for the fact that players can still play Sub at a high level, and it’s still difficult to do… that is obvious. There are many factors besides excellence in one’s class that are necessary for excellence in arenas, and that includes making the correct reads, situational awareness, good communication, game knowledge and strategy, and still mechanical skill in optimizing damage. But my point was never that being a R1 Subtlety Rogue isn’t hard, my point is that playing Subtlety is no longer cool, fun, or interesting.