"Priority" positions are dynamically chosen based on which positions need more players throughout the server. In the example below, there are already too many players vying for middle and bottom, so you'd have to swap one pick to a lesser-chosen position in order to enter the queue. 2–...
In order to keep the queue popping quickly, one of your position choices must be a “Priority” position. These are positions that are most needed by the current matchmaking pool (the UI will tell you which is needed). The intent is that you get your first choice most of the time, but...
The intent is that you get your first choice most of the time, but there will be times when you have to play in a Priority position. This is something we will keep a close eye on numbers-wise and tune accordingly. Here are the specific rules for different party sizes: Solo 2 unique ...