I think there may have been a balance patch since the last time I played this game. There's a whole new "stamina" mechanic and I'm not sure I care for it. Your major non-magical abilities have a stamina cost and stamina builds up over time.
I get what they're aiming for. The new system prevents you from frontloading your most powerful attacks and forces you to plan your tactics over the course of several turns. The problem is that I actually liked unleashing all my best abilities on the first turn, and so far my battles have not lasted long enough for extended planning to come into play. I'll have to wait and see what high-end combat looks like before I make a final determination, though. My favorite part of the game is when my heroes are hugely overpowered and can take on giants and dragons and demons from before time and whatnot. If I can still get ludicrous power interactions and over-the-top character stats, I'll be happy. If I find myself bogged down by excessively punitive "game balance," I will be unhappy.
Other than that change, Legendary Heroes is still the same game I remember. It's more similar to the original Fallen Enchantress than I remember, but it has a ton of little improvements that are not huge game-changers individually, but which make the whole experience more enjoyable. For example, you gain new heroes by reaching certain thresholds in your "fame" resource, ensuring a steady stream of new characters to play with (whereas in the base game, your acquisition of new heroes was mostly up to chance). Similarly, the leveling up system is just outright better, as it allows you to visualize and plan your characters' advancement through one of four different hero classes. And there are new spells and quests and treasures and monsters that are nothing on their own, but combine to give the world a lot more life (when, in fact, the exploration and setting was already the strongest part of the original).
I'm looking forward to the rest of my time with this game, though. For all that it is not a revolutionary overhaul of the original Fallen Enchantress, it is still the definitive version of the game. I just can't wait to get another dragon.