Of course the LSAT isn't perfect, no test is. However, as you point out, the LSAT is a dependable predictor of academic aptitude (the exact thing it is designed to predict!). It stands to reason that in most cases a student with a high LSAT score will out perform those with lower scores. The LSAT is not supposed to approximate the law school experience, it just measures ability.
To the OP: don't go to ANY law school unless you are prepared to spend all three years there. Once you start you will quickly discover that law school, whether you're at Harvard or Cooley, is nothing like college. The competition is intense and it's very difficult to predict how you will perform, especially if you're coming in with less-than-stellar numbers.
If you are prepared to spend all three years at Cooley anyway, that's a different story. Research the school's curve and contact the schools you'd like to transfer to. Most importantly, be realistic about your gals and options. If you start law school on day one expecting to be in the top 10% and transferring, you will likely be disappointed and frustrated. This is nothing against you personally, it's just the cold, hard reality of law school. My law school had a brutal curve that made it very difficult to transfer, and I suspect Cooley is the same.
Be realistic about all aspects of law school, not just transferring, be prepared, and be informed. If you do that you'll probably be alright.