The hot hands toe-warmers have been pretty abysmal for me as well. I don't think there's enough material in them to allow them to create heat in spaces that do not have very good airflow. The handwarmers in shoes work better but are still much less effective than when used in open air or in gloves.
I did discover that placing the handwarmers on the major arteries in the front and rear of my ankles between my sock and shoe-cover, seems to work much better than trying to warm my toes. They seem to get additional airflow and stay hotter as well.