I think 3 teams is OK, and it's one of the few things that actually stops 1 team from being rofl stomped for 10 minutes.

Also, there's no real active collusion, these things will just happen from time to time where two teams have the same thought process. They aren't really colluding and nor is there some grand conspiracy. Some teams will also have no real coordination nor self awareness into what's going on, which inadvertently leads to feeding a team or group of players.

What you're experiencing is simply a team that isn't coordinating.