Instead of “what are their chances?”, I would ask “what are their choices?”. I would call the tone grim if the characters always take the heroic option, but the choice is always between “50 people die” and “100 people die”.In my definition, that grim.
The player's characters are always rising to the occasion. Otherwise there is no game to play.
The question is what are their chances? How dangerous are their normal challenges relative to them?