Well, the only things that I recall being speculated are:
-1v1 between partners
-2v1 partner vs enemy
-2v2 pair vs pair, but won't work cuz we have an odd number of pairs...
Now, the vague "close" response to my theory indicates I am at least partially correct. With that being said if:
A) The part about teams is correct while the mock dungeon is incorrect, then the only conclusion I can draw is a battle royale.
Or
B) If the opposite is true, then the pairs are opponents and will be competing through a mock dungeon.
Of course, I could be missing all marks...