you have to accept 1 fact, only the knight will survive, because the archer and the mage will die if alone (they love to be alone), and may almost die even if they are with the knight, so 2 unlucky 50/50 and they die
This was one of the first ideas before making this, each hero going on its own way, and such as mage just dies. Plan to add in the future that you can make a pair of heroes and they go together, or something like this to mitigate the luck