I commented last year about the multiple LOTRO PvMP battlefronts:
One interesting outcome is that most people win most of the time. The side with more bodies usually wins, or the winning side quickly becomes more numerous as fair weather friends join and leave their respective teams. There can be multiple fronts, so 75% of the freeps might be at the lumber camp beating 25% of the creeps, with the reverse happening at the mine: both sides had a win, and most of the players on each side were part of that win.
This weekend, I had the opposite experience playing Team Fortress 2. Two times in a row, playing Gold Rush, I was auto-balanced to the losing team within the last minute. With players joining and quitting the teams, you have the opposite effect of PvMP, where the majority of the players are losing most of the time. There is a cap on how many people can join the winning team, and if you are winning, you are less likely to quit. There is never a cap on how many people can quit, so a lot of the losing team leaves, which cycles in new people who also get crushed 5 seconds out of the spawn. Why did no one mention on chat that there are two Heavy-Medic pairs at the spawn? They all quit, and a quarter of your team just joined the map. A quarter of your team is loading in or out while the winning team makes more progress. If people are not joining for the losing team fast enough, they will be taken from the newer players on the winning team. Hit tab, and you will see one or two high-scoring players on the losing team (who have toughed it out), and no one else there above 50; on the winning team, if there is anyone below 50, he has scrolled off the scoreboard. There is no way to overcome this, because half your team will be dead or loading in as you join the losing team, and continuously from there on, so you cannot make any progress. A previous night on this server, I saw the blue team fail to ever move the cart. After a few minutes, no one survived as long as five seconds outside the base, and most never made it to the doors.
My new plan is always to check the scoreboard before joining a team. If one team is way ahead on points, there is no point in joining. Even if you can join the winning team, you will be auto-balanced away. You could try to stay long enough to reduce your chances of auto-balance, but you’ll probably get kicked for a reserved slot.