In the Demigod Journals Brad has mentioned some details on the upcoming patch GPG is working on. One of the things that will get improved is the ingame netcode (as opposed to all the lobby netcode changes which have been happening before).

Just wait a bit. Hopefully next week (the one that starts in about 2 hours and 17 minutes as of writing this) the patch gets out. Depends on how much their QA department complains

Yes, I know it was me who dropped connection... but the reason I posted about it here is that the game itself should have figured this out and returned me to the menu.

Hah! I believe that was me the second time you experienced that Eo. I had decided to host my own game, it was a 3v3. First 1 of the opposing team members dropped from the 30 second time out. Then a couple mins later another from that team. Shortly after that the last person timed out. It was going to be a regular compfest at that point. However a member of my team dropped and I was like WTF. We're the only ones left. Hopefully it's all fixed soon.

Well, the third time this happened, the first player to disconnect was on our side and we were winning the game.

Then, one on the other side disconnected, but it was a 5v5 game, so I didn't think much of it.

But later in the game the chat went all silent, and when I looked at the scores, all others had ping 0, and I hadn't seen any more disconnection screens.

Seems this might be getting a fix in 1.01:

"If a player loses connection with another player (or one player with a group of players but not all) only 1 user is disconnected instead of multiple."