The only real way I can see to curb people bailing on the mentor roulette is if a) the daily reward was actually worthwhile (meaning something that isn't just some lore/scripture) and b) bailing burns your daily reward so you can't just eat the penalty and try your luck again 30 minutes later. No matter how bad you make the punishment, it won't incentivize people to stick out dungeons they don't like, but an actual worthwhile reward that they can't get if they bail will.