Matchmaking not pairing the only two teams of 5 in a queue

I sat in solo/duo queue today for a good 3 hours waiting for find a team, and eventually was able to get a full 5/10. One of the guys on my team said a friend on his list was also in solo/duo and had found 5/10. We waited about 30 minutes to get matched against each other before people on our team had to leave. There must be some issue with matchmaking for the only two full teams of five in a queue to not get paired against each other.