I think that this will be fixed when Idle comes out of beta, or even before that. And trust me, Fizzer reads this :) Hi Fizzer!
There still should be a minimum # of players, but based on the first few games that Fizzer manually started. battles work perfectly at 7 players. Based on that, I guess the minimum can be set at 6.
Running battles with 6 players works a lot better than running them with 30 or so, where everyone gets disconnected and a lot of bugs pop up. (But I'm sure Fizzer is working very hard to get that fixed asap)