Well - however it works, three things are fact...
1) We were missing one party member when I left.
2) Six people had already left (first two left at the same time, then a third - once it refilled, another left, then the other tank left, and when the 6th person left, i left).
3) I got a 30 min penalty.

The guy that was 'missing' when I left did have ?? on his name - and it wasn't actively searching for a person - maybe a disconnected person doesn't count.
In either event - the solution is simple - don't queue for MSQ unless you need it.
As a person that has tanked it every day since the day I started playing, I can't help but point out my dislike for the change.