I'm running a Mystical Theme tomorrow with the two smaller 2015 Con Exclusives. My question is if both Doctor Strange and Felix Faust were both to roll the Grey power "Your force may be given any number of non-free actions. For each non-free action beyond your action total you use, decrease all opponents' actions total by 1 (minimum 1) on their next turn." Does/ would the reductions stack.

I see no reason they wouldn't.