Ok, I'm just going to come in here and do what I have to do. And that is completely buckle the foundation of this idea to the ground.
From the perspective of a tank or healer role, nobody would ever join a new party. I read your post in the other thread, and what you don't understand is that healers and tanks are a limited resource. But, let's break this down.
Let's say there are 50 Tanks and 70 Healers and 200 DPS in the queue, with this feature enabled, all are waiting for WP or AK.
200 DPS are marked for new party or "any progress" (The queue time for a DPS is already around 30~ minutes for a new group. Checking for in progress on last boss as a DPS? Good luck waiting 3 hours for a queue pop. Pretty much expect all DPS to queue for "any progress")
Roughly about, hmm 45 Healers, maybe 50 Healers are queued for 2/4+ or 3/4~ progress. I say this cause people who play healers are generally moderate about their demands, plus Healing queue times are around 5 minutes or so, sometimes instant. So it's fairly quick.
90% of ALL tanks will queue for final progress. You know why? Cause their queue time is 5 seconds on average. You don't play a tank, so you don't realize just how simple it is to queue for any dungeon as a tank.
Now that leaves a handful of tanks, a bunch of healers and well pretty much every DPS job left over to form new groups.
Let's analyze from now.
So, with barely any tanks and healers to form new groups, how many groups on average are going to have some person leave on the very final boss? Not alot, you know why? Cause queue times for new groups is going to skyrocket. Get ready for DPS queues being 1-2 hours, because all the tanks and healers are queued for final progress.
But... with such high "new group" queue times, the chances of getting a queue with "final progress" is very low.
The whole concept is flawed and basically sums up to this:
0 Positive
Infinite Negative
The solution?
Remove view of progress entirely, except for time remaining or put a penalty to people who are constantly withdrawing to search for "final progress" dungeons.
If the above is not done, then DPS are completely left in the dust. And guess what? DPS jobs are the majority and have the worst queue times, so things need to be done to satisfy them. If not, you are neglecting 70% of your playerbase.
That's it.