The Swain nerfs are nice.......

but they aren't going to change his ban rate until his natural synergy with ROA (or more specifically catalyst) goes away (or is more costly).

The amount of uptime Swain can have on his ultimate now with catalyst restoring mana as he takes damage (which is quickly healed off both by catalyst again and his ulti) is completely nuts and not even grevious wounds are effective in combating a Swain when he gets rolling.

So until you address the swain that has massive uptime on his ultimate and has access to really good waveclear, he is going to continue to get banned (or if he actually gets into a game, over perform).