So there is a blog or forum that is feeding someone asshats ip addresses.

So a wow forum/blog for example you logged into would give them your ip address, from there they would target that address. Getting that address to correspond to arena people would either mean arena specific blog or them knowing something specific about you. Them knowing something specific about you would mean you filling out a your server/guild/character name someplace (like ej, team/comp signature app, or using a tool like tune by reforges, etc)

There is no way someone playing the game is going to decide they want to ddos you and then attack your router. Baring them living in your dorm, house, or similar.

My guess if this paranoia is for reals is that a blog got hacked and they don't know it.

If your also running bit torrent software downloading 'stuff', these attacks happen often days after you stop downloading and pack up the client and switch ports, even if you pick up someone elses ip the attack is still there. That's jut part of that game. I would think that is the real source of this. The attacks on torrent downloaders is essentially a test bed on how to attack people, with the excuse that they are torrent downloaders.