I understand and agree that the swear filter could be better. Though, that being said, you have to think about this from other points of view. You can't just stick any and every word/combination of letters into a filter. It makes for a messed up looking chat. Just like some suggesting that "ez" and other things be put in the filter, then players wouldn't be able to use many/any words with the letter combination that included the letters "e" and "z".
So, you can't have every single bad thing filtered or else no one would be able to chat or the chat would end up mangled and difficult to read. I think things are alright as they are now, if you see someone swear, then give them a warning. If they continue afterward then you may report them. I know this can be difficult in places such as 1v1 duels but if you get in another duel with them, they can be warned.