I think recording the match might be the way to go. Even if it means not playing your best, at least you'll have CLEAR evidence that they are cheating. Naming and shaming on the forums is strictly forbidden (and will result in your forum account being suspended or banned), but I think a video would suffice as evidence for SE to take action. Maybe to be on the safe side, you can have it as a private video and provide SE with the link.

Cheaters take the fun out of the game for everyone, whether you are on their team or not. Even worse -- they take up one of the few prestigious top spots (if they are top 10), and it's really not fair to people who work hard to abide by the mechanics SE has put in place.

I have my fingers crossed that SE is observing people who have been reported for cheating or outright abuse (intentionally throwing games). If they are, then it's only a matter of time before there are blanket bans for all these people. People who are banned for PvP cheating/abuse should also have their rankings stripped, freeing up spots for legitimate players.