You can ask them to dismiss you, but at that point you're asking for some to be on the balance if they decide to mess with or not.

unless the emergency or occurrence that had to be dealt with was shorter than 30m, I doubt you'd see that unless you didn't plan on afk for abit.

I understand that pain, only once, had the game flagged me for 30m, but that's cause I left a match a millisec before the Results came up in a banner.
[for those in pvp, once you see victory or defeat, you're cleared to exit. but don't risk the timings unless you know exactly when it unlocks the match to freely leave. a few seconds could match you up differently, but it's hardly much change]

it is what it is, go again..,
and ask devs to keep the penalty up for all users. that way players get pushed to use disband, and don't have some "take one for the team" in what they think some others will leave, or won't leave with them.
They can improve this system at the very least, so asking for a dismiss isn't harmful or out of the question, or interruptive to the progress of instances.