It could/should be a bit more, yes, but you also have thousands of representatives in the state governments and that isn't working out much better with respect

It could/should be a bit more, yes, but you also have thousands of representatives in the state governments and that isn't working out much better with respect to gerrymandering. The advantage with the mixed-member system is that you get to elect both a representative and a party, so even if you don't end up getting the representative you've hoped for your vote still matters.