
So Arena Claus came down the chimney today, and I thought it would be interesting to compare which champs I got and what my rank was in those arenas to see how much the anti-bot anti-cheat systems that Kabam implemented impacted those arenas. For the seven champs above, these are the ranks I achieved between the two rounds:

Based on these numbers, it seems like the number of places that were nullified due to Kabam's improved anti-cheat detection system was at least 17 places for Voodoo, and an incredible 68 places for Void (out of top 100). For 5* featured champs, it was between 44 places for America Chavez and 96 places for Hercules. I also received a champ from a basic arena (DDHK) due to an (at least) 47 rank adjustment.
Given how many places were touched in the top 100 and top 500, this implies hundreds of bots and other cheaters detected and either removed from the standings or banned from the game, as most bots were unlikely to be consistently entering the top 500.
In the 12/16 arena I managed to get 113, but did not get a selector as compensation. Apparently starting around mid December, Kabam's real time detection became good enough that the back corrections did not detect as many if any cheats from that arena moving forward. So presumably arenas beyond mid December are likely to have less (but not necessarily zero) cheating.
Apparently, I got an AV even though I actually hit the 500 rank in both rounds. When I reported this I was told was that this was likely due to that arena having a real time ban that put me into the top 500 that wasn't counted in the correction pass, making it seem like I placed just outside of 500. So it is possible that a couple of players in every arena right on the borderline might have gotten a bonus 5* champ.
Anyway, while this doesn't mean Kabam as eliminated all bad actors from the arena, hopefully this means that the arenas will be much fairer to grinders than they have been in the recent past. And I happen to know that this activity was triggered in part by discussions Kabam had with the CCP, and some of that brainstorming almost certainly led to this result, so players have both Kabam and the CCP to thank for this improvement to the arenas and compensation for the effects of the bad actors in the arena (long may these bad actors burn in heck).