The real test for your hypothesis will be what happens the next time the Republicans get the presidency, the house, and 50% of the senate.
If the senate still acts as a moderating force (and doesn't push through extreme new legislative and judicial changes that tilt the system to further their advantage) then the wisdom of the current system will be empirically validated.
If the senate still acts as a moderating force (and doesn't push through extreme new legislative and judicial changes that tilt the system to further their advantage) then the wisdom of the current system will be empirically validated.