just had a talk with one of the devs today and the matchmaking formula has a hard cap based on your ELO, meaning that if you are particularly high you won't ever meet certain low ranked players. I've the same issue and i can't play 300 AP...i stayed 15 min in queue and left (there were at the very least 3 people queued there as well...). He stated that they are looking at it and might be modified
EDIT: it seems i cant even play at 400 AP fast enough...lol. I'm basically stuck unless some other high ELO player comes in. I guess the hard cap is a bit too high...i mean it takes me 11-12 minutes to find a match ...during the evening, not even at some crazy time =/ i feel trolled by Cyanide