If you finish with the same record overall, but one team had an easier schedule, that seems a reasonable tiebreak
I get that we don't like it, but I can't really see a better way
It's also something like the 5th tiebreak, already after whether you beat better teams than the other tied teams. At some point, if everything else is equal, it pretty much has to come down to how tough the schedule was overall.
Like someone else said, not satisfying, but somewhat unavoidable with how large conferences have become