There really is no such thing as "breathable rainwear". However, if you look at it another way, there is at least one solution to the stated problems. If you ask what is the most ventilating garment that keeps you dry while riding in the rain, my answer is a combination of a hood-less rain cape, a helmet cover and effective fenders on the bicycle. That combo provides all the rain protection I need. The cape is waterproof but open enough to get ventilation.