That might be the reason why my matches are always kind of unbalanced. So USF rank 10 = OKW/OH rank 12?
Possibly. Sadly, relic doesn't show us our elo, only the ladder standing... So we will never know for sure. What you can do is go to the last page of ladder and see how many players are ranked in it, that way you can get the ratio to multiply standings by. This is not perfect (it assumes linear dependence between elo and rank, while sorting is not linear dependance in any way), but better than what relic serves us.
The important thing is though that it doesn't mean that your matches are imballanced - it means that you judge a ballance of a match by flawed indicator (the "rank").