123a,
Your argument against using light as an option could be used to argue against anything, OC, 9mm, 5.56/.223, whatever. Nothing works every time. Never expect anything to work the first time, or one shot. The light just gives you another option that hopefully will work, but at the least it can provide a distraction while you or another person use a different option.
I think light is most effective in very dim locations where a person's eyes are adapted to the dark. A bright light then will usually cause pain, blind them, and when you sut the light off a second later, they will no longer have any night vision, and hopefully a few distracting spots.
Add a can of OC to your daily carry to give you one more option. And you don't sound too crazy. HK, Benchmade, 9P, Sabre (until I find a replacement cannister for my ASP Key Defender locally since I refuse to pay as much for shipping as the can costs and/or a can of Fox).