About multi channeling and mini-dungeons

It doesn't seem that way, because more often than not I'll end up in the same mini-dungeon over and over again even during 2x events and stuff.

If more people enter than leave while you're inside, you'd end up in the same place as long as you exit and re-enter before anyone else does. You only switch when one of the rooms "below" yours opens up while you're inside, or someone enters yours while you are outside.