Your feet are going numb, you really think you're "good" with stock insoles? You're completely locked into a position and your ankle is relatively immobilized in your boot. This means you don't have the range of motion necessary for proper foot action so your foot can't support itself right. Getting after market insoles with a good stiff supportive heel pocket keeps your heel in place and supports it, thereby controlling the rest of your foot and providing the support it needs. In every day life I support minimalist footwear as I think most shoes are too supportive and don't let your foot do its own job. But with shoes your ankle is free and you have your whole range of motion to let your foot do its job. So in shoes you might not need them, in big stiff snowboards boots you do.
So keeping what I have, what kind of insoles could potentially help?