For the most part it’s not bad when you consider that there’s been 60+ unique units released so far for the game. The balancing is pretty good and there’s defiantly evidence of a lot of play testing. We were actually discussing this last night, and we tried to name chars that we feel are totally useless and only one or two came up. We even tried to name chars you can’t live without and again only one or two came up. For the most part they are easily balanced by minor point value tweaking.
It’s just that unlike a video game, Heroscape can’t just patch its mistakes. Sometimes at first glance a character may seem over powered, then when you go back and read the details of their cards closer, there is often little gotchas that knock them down a few notches.
But your are right, the map has a lot to do with the gameplay, and a poorly matched draft to the map could spell death to your game. Not to mention missing tiny details on your drafted characters cards can also spell death to your game (like what happened to me last night)