3 heroes? WTF?! lol. Dang, usually you work on one hero and then a second near the end. A third only for fun usually.
Chimuras? Dang, must've been a "long" game. Usually you wouldn't be able to get that far nor that many if they know what their doing. My strategy is pretty much archers/huntress armies. Keep coming at em, don't let them expand, and don't let them get those chimuras.

While you control the map w/ your army, expand and upgrade and just keep building. Tech up slowly, since all you want to do is upgrade weapons/armor for archers/huntress. I only go for Chimuras if they don't have any anti-air men and if its a long game.
Getting +7 gold instead of +10 at 30 men, due to Upkeep. Blizzard put this in so that you don't have a huge army just sitting around always building up. Instead it forces you go around and fight. It goes to +4 later on, but I don't know at what number. I'm like 8-2, following this strategy... of course those two losses were due to sucky partners, but oh well. This game is so heavily dependent on your partners, which is the only downside to me. If they suck, you're pretty much screwed.