I think I saw on Discovery that there is a difference in matter/energy in what is being observed and what the current estimates are by 10*120. That is a 1 followed by 120 zeroes!
Unless there was more matter than is being observed, the expansion would tear the universe apart. I think the physicist have some fundamentally flawed theories when we see such numbers.
Dark matter/energy is as you say maybe a "crutch" for the current popular theory.