You make some good points, but karate isn't always about blocking and punching.
Take the Wado Ryu 'deflection punch' for instance, where the outgoing punch itself deflects the incoming punch before landing in the opponent's face. Extremely fast and efficient as no time is wasted on the block.
However, I believe in studying all forms of defence. I know acupuncture points that can be used very effectively to cause severe pain. Also, at a young age (16), I was on our local Air Cadets Unarmed Combat Display Team which taught me some very different techniques to those I later learned from karate.