The system does not gaurantee N vs. N sides.
It balances both sides based on their XP. 2 good players vs. 3 new players and so forth. Don't assume just because you face 3 opponents that you're going to lose.
This is just insane. Demigod is certainly balanced for having an equal number of people on each side - that's why there are flags.
Do the people on the 2 people side move faster or cap flags faster? Do they get 50% increase gold? 50% more creeps? No? Then you can never balance the game for people being "bad."
Split the 2 "good" people onto both sides and split the 3 "bad" people onto both sides, and get a 6th. Uneven matchups in Demigod are just not feasible to win assuming everyone knows how to play. If they don't - match them with people who don't.