I've tried both options, first or last, it "always" match my human team somehow... I think it's a "bug", since some other times , it matches one of my other team.
Was it the first team you made? It may be going on order of creation. Its possible that queuing with multiple teams is a cascading thing - if it can't find a match for one team, it looks for the next, and so on... rather than finding the most compatible match across all teams.
I'm on ps4, I'm pretty sure average is more than 250. It's not rare I play a match with 700k+ difference... I was pretty happy to see that they decided to reduce it to 500k, I was on the edge to make that suggestion. ;)
I hate to break it to you, but if most of your matches are 700+ difference, the 500+ maximum isn't going to fix that, it's just going to mean you won't be getting any matches at all most of the time. The distant matches were due to there being no better opponents available.
Now, if it IS a cascading system, and you have multiple teams of varying TV level, then it might work out for you. If its not, and for anyone who doesn't queue with multiple, diverse teams every time, it will end up with fewer matches played overall.