On my data center of Primal, I see a lot of these party finder ex primal pugs. I know what people will say: "If you don't like them, don't join!" And that's what I do, but I just wanted to show the math as to why they aren't a good idea to join. Also, they are basically a low key pyramid scheme. The only person who benefits is the leader.
The drop rate on the mount is about 5% for the new ex primals or possibly less, but lets be generous and say its a 5% chance of dropping. This makes it a 1 in 20 chance that you will see a mount drop. While I realize "mount lootmaster'd in order of join" sounds like it would encourage people to stay until they all get one, let me explain why that won't even come close to happening.
So lets say you get 8 great people and every time you queue in for the ex primal you get a kill 100% of the time. Also, lets say that including loading in and out of zone, that getting a kill takes you about 10 minutes (probably less but people will probably inevitably have bathroom/drink breaks). So with a 1 in 20 chance, just getting one mount is going to take you about 3 hours and 20 minutes on average! This is where people might say "Well we are going to stay as long as possible and get as many as we can!" To get 8 mounts it's going to take you 26 hours 40 minutes on average! How long is this pug probably going to last you at best if everyone is good? Probably 2-3 hours before people start to bail and the leader gives up or passes lead (probably after they get their mount).
Who is the only one that is going to get a mount? The leader of the group and maybe the 2nd one that joined in a small chance. Of course you could run 3 hours and get nothing or could get 3, it's all chance but the odds of getting more than one are pretty low.
So this is just a little Public Service Announcement... :P I know most of you probably already realized this because I see these kind of parties filling slowly (probably with people that don't really care about the mount). But, I wanted to give information to those who maybe don't realize what the drop percentage actually is.