Of course the importance of checks and balances in our government is a well known concept as discussed in Federalist No. 51. What I had not previously realized was that splitting the Congress into two houses was a part of the effort on checks and balances. I had always understood that choice to simply be a compromise between the power of large state and small states.
In republican government, the legislative authority necessarily predominates. The remedy for this inconveniency (sic) is to divide the legislature into different branches; and to render them, by different modes of election and different principles of action, as little connected with each other as the nature of their common functions and their common dependence on the society will admit.
Today some may argue that the legislative authority does not predominate in our government. Closer inspection of our government shows that it does still dominate which is why the concentration of interest in the executive branch by individuals and news organizations is so effective at confusing the electorate and allowing a Congress with 10% approval rating to have a 90% success rate among incumbents. (At a state level the same results can come by focusing on the governor over the legislature.)
Those who would argue that Congress does not dominate the actions of our government can only have an argument if they claim that the parties have come to dominate the government rather than arguing that another branch of government has come to dominate.