With ver 2.3.9 if a player joins a game with high ping the host will loose the lobby server and have to rehost, happens often to many hosts. So most hosts kick right away for high ping. if you watch the lobby server you will see the lobby server gone first, then maybe some players will drop because 2.3.9 seems to be delayed in this way.
With 3.1 rc2 if a player joins a game with high ping the host will loose some players that are connected with good pings but the host does not lose connection to the lobby server. Actually I've noticed this since 3.1 beta 10 for myself but didn’t really pay that much attention to how other hosts do it until now.
If you watch hosts that are able to host open 10 player games you will notice they don't talk much and they must have the mouse right there ready to kick the instant there is a high ping or * no ping because they do it fast. And if they don't a few players will vanish from the room. For me I don't keep my mouse right there, I'm talking (typing) or looking at my self made buddy list so it's preventing me from hosting the way I want to. Do we really need to allow connections with pings up to 4s? If possible an auto kick programmed in for the lobby room with a max value of 700 or 800 ms would be really nice to see if that resolves it because I think many are still having problems hosting, including me. I can host if I keep my mouse right there too, but I would have to stop talking and not do anything else except wait to kick.
Actually if this works then it could be adjusted to about 400 ms and the kick available to the host would not be needed at all except for a few rare circumstances, and the room could just be closed in those situations. I host players up to 500 ms ping without any problem, but 400 ms is safer.