You are taping to wood, so it really wouldn't matter, plus if your heat tape is damaged enough to shock you through the aluminum tape it's time to replace it. Maybe the stuff you are using is different, but every time I've heated duct tape it resulted in a sticky miserable mess when it came time to remove it.
At the end of the day I guess it really doesn't matter though, it's not like the duct tape is going to be a fire risk. To each their own.