So, should we focus on multiplayer? Honestly, it seems to me that most Heroes players (nowadays) prefer interesting mods and single-player scenarios. IMHO, of course, but you don't always have time to play with a friend online. But here – whenever you want – all maps are open for you alone. I don't even know.
In any case, as I said before, the balance in single-player is much more dependent on the map itself (scenario, scripts). But for multiplayer, the game's own balance is crucial.