I think the 30 minute timer is enough.

I've had situations in the past arise like an unexpected work emergency that required that I leave a dungeon early. I know others can have things come up with their kids suddenly. Despite best intentions, life can happen.

I think they have a 3 strikes rule or something per day? I don't recall but isn't there a counter when the lockout gets worse if you keep leaving? I think that is good enough. I've rarely had to wait more than a minute or two when someone disconnects for a replacement.