Actually you are pretty right. There are very few hackers/cheaters who are actually good. Skilled enough to defeat hackers in this game and sometimes you wouldn't even realise you beat one until you look at his gear.Although some hackers/cheaters feel like Legit players unless you look at his affixes but most aren't a huge issue but it's still good to report them so they don't accumulate so much.
I mean I have faced cheaters/hackers who are very hard to defeat and definitely deserve to be removed but thankfully they are very few and rare. Still they happen to be the hardest to ban in some scenarios and can annoy many players . I think the chance of a hacker who actually knows the game very well is extremely low, like probably 0.1% or 0.01% maybe . Usually legit players stay legit for a while and know alot but maybe there's that one guy who becomes a hacker/cheater with some knowledge of the game after being legit for X months and no longer legit for whatever reason.
Compared to other games I've played, this game is pretty darn balanced when it comes to facing hackers/cheaters as you can skillfully beat them but there have been some cheaters who are very hard or sometimes a group of challenging cheaters due to the modifying of certain eternals to allow them to be that extremely strong or Tanky. Honestly it's awesome that cheaters aren't as bad as they used to be in arena as it shows how far we have come in skill level and balance but reporting all we can is the best to do.
If no cheaters were banned, this arena would be way to filled of cheaters by now but it's great that it isn't. as filled.