Its worth considering the problem isn't arena trap but the sweepers themselves, specifically clamperl. Its odd to say that arena trap makes clamperl op when even without arena trap its still op. With little to no help it still beats tentacool and chinchou.
Gastly is a touch easier, with a few fat boys around in porygon and lax as well as im sure a couple pursuiters but those will lose out to trapinch, they aren't as afraid of diglett.
Foo is fairly manageable even now, with koffing, probably some ghost boys, budew, does foongus get regen yet? do people run zubat? i couldnt find usage anywhere blame munya.
tldr; ban clamperl first, then suspect test trapinch, then suspect test diglett.