I find it depends who you're fighting. Plus me and my partner don't use three heroes, but four - two each. We played with one each for ages but after a while decided we knew the decks and stuff well enough to be able to cope with an extra hero each.
Anyway, he plays Legacy in nearly every game. I've quite got into playing the Adept so he comes up quite a lot. I have a permanent fondness for the Wraith, while he likes Tempest. He also plays Bunker fairly often, and Haka. His favourite character is Fanatic but he only seems to play her against Apostate. Some games we just get our arses kicked while others we totally flatten the opposition - it's not just a case of which combo you take of heroes, villain, and environment, but which cards come up. We had our arses handed to us on a plate by the Matriarch a couple of weeks ago, when fighting against her in Atlantis. We were doing okay until two Leaking Rooms on the trot meant we couldn't play any cards for two rounds (I was the Adept but Sarabande of Destruction hadn't come up yet :P), and then I think she played a Horrid Cacophony or two which took out all my good songs and whatever else was left on the table (except equipment, obviously, but Huginn dealt with some of that later).
In another fight (same villain, same environment - we roll for both of those but dammit we turned up the same combo again), we had two Mystical Defences come out within a couple of turns of each other (followed eventually by all three Krakens), before we'd properly got our defences organised, which meant that the birds were constantly being taken out and we were getting smashed by the psychic and toxic damage (yes, both Carrion Fields were out as well :P) as a result. That game didn't last amzingly long.
Then, this weekend, we had the same combo again! Matriarch in Atlantis. And I think the team we picked (we roll for villain and environment but choose heroes after that) was the same as we'd had for one of the fights last week - me playing the Adept and Haka and my partner playing Legacy and Bunker. I managed to eventually get the Mask, both cohorts, and lots of Fowl under Savage Mana and unleashed it to finish the fight right after Bunker let loose with his Omni-Cannon. So that was cool :).
In another fight, also this weekend, we had Citizen Dawn in erm…somewhere. Megalopolis, possibly. Anyway, again Haka finished it off with a smash from Savage Mana. That in itself would have done something like 17 damage (he was buffed by Legacy and the Adept as well), but he's also poured his entire hand (around 19 cards) into Haka of Battle during his Play phase, so the total damage for that one hit was something like 39 - we didn't bother to work it out exactly - Dawn only had about 2hp left. But I wanted to erm, be sure she was dead, or something ;).