It takes 2 turns for Selise to reach Ares and to heal him (assuming she dashes for 60 feet this turn, else it'll take 3 turns). If Ares rolls a natural 1 with the next saving throw then it's already game over for him since a natural 1 counts as 2 failed death saving throws, putting him at 3 in total and at permanent death. Considering our current bad luck when it comes to rolls, I'm not sure we want to take that risk. It's only a 5% chance, but Murphy's law comes to mind.