It's not that simple. For one thing it matters what level you are. Also, all ratings have diminishing returns so you can't calculate it's value accurately per point: each point is worth less than the one before it.
People discussing tanking at sithwarrior.com are saying that defense is stronger than shield or absorption, but you can't stack one stack too heavily because of the diminishing returns.
That is what I thought, btw lvl 50, but I was just trying out some napkin math without a DR formula so that would be why my results weren't correct.
Thanks for the reply.