i think you are underestimating Liquid and overestimating the ai in those rays. i have no doubt that fox could have taken all those rays out easily if he had been in that situation instead. raiden was fast enough to take them out, and you cannot argue that raiden was faster than fox during that fight, cuz that is ridiculous. plus, rex was just designed better for combat, everything that rex has is available right away, ray has to move its arms to be able to use its machine guns, and has to open its mouth to fire its compressed watter. rex has everything right there, it can shoot the laser at the same time as the Gatling Guns if it wants.