I cannot say for most of the DCs, but I think Light is in pretty good place aside from having small-ish playerpool. I haven't seen blatant cheating aside from some questionable cast times from some WHMs in past Seasons, but I think they can still fall under the player just having excellent reflexes.

I'm not part of the discords and such so I can't confirm existence of any secret cabal. There were handful of the top players previously in some of the largest PvP ones, but I think its more about playing together other games when the queue is dead.