If the problem is people roulette-shopping, surely a potential solution is taking away roulette bonuses for the day rather than duty finder use. If you're the first to leave a dungeon, you lose that day's roulette bonus. It's still entirely possible that it would negatively impact some people who had to leave for legitimate reasons, but roulette bonus isn't that important and losing it doesn't make the game unplayable for the rest of the day. And really, an IRL emergency is so much more important than tomestones that it wouldn't register as an annoyance beyond 'eh, bummer' if it came to that.

Really, I think 'more punishment' isn't the answer. A better way to think of it is to consider the roulette reward what it is: a reward for agreeing to run whatever dungeon you got thrown into. Losing it isn't a punishment, it's just not getting a reward because you didn't do what was asked of you.

In response to scarletfoxxy, I don't think it's unreasonable to expect people to commit to finishing a dungeon once they enter. I understand that tanking a long dungeon can be very stressful, but we're not talking about forcing people to do it. These are people who specifically queued up to do that dungeon because they wanted to. Or people who queued for it via roulette, with the understanding that the roulette bonus is a reward for sticking out whatever dungeon it throws you in. As far as I'm aware, short of accidentally queueing for the wrong thing there's no way to end up within a dungeon without first saying 'yup, I sure do want to be in this dungeon'.