Teleporting a mon in for Pex and Pex switching out hurts the switch in but helps Pex with regen doesn't it? And your second thought "Pex isn't a suspect because there are other busted mons in the tier" isn't helping your argument much either. Not that I have a prob with pex or even mentioned it, but your second thought is pretty revealing.I think that's fair, but the increased ease of pivoting stuff in via Teleport, especially in conjunction with Future Sight, make it easier than before to deal with Pex since there's more ways to bring in breakers vs Pex that avoid taking a Knock Off or Scald on the switch in.
Mind you, if the remaining potentially-busteds (Mag, Spectrier for sure will be suspected at some point IMO) leave, Pex might prove to be unhealthy (if not broken) and warrant a suspect.
Anyway, recently I was thinking Offense is going to run out of tools before Defense in terms of optimization. Defensive mons can keep re optimizing their spreads as the threat list gets reduced by bans and offensive mons have more or less shown all of their cards already. I wonder which defensive mons are going to drastically change their spreads or how defense is going to re optimize after the next ban.