Heroes are definitely overpowered.



I'm on turn 120 now and in systems I have heroes assigned the production, food, science and dust bonuses are around 10 times higher than in systems without heroes.



This is a issue that should be adressed.

The same screen where you hire new ones, you can clone the ones you already have. The clones have all the traits, abilities, and stats of the original, and aren't much more expensive than hiring a new hero. Although I suppose it's worthwhile to get someone who will specialize in something different.

:O How do you clone them?



They do level up very quickly indeed and can give insanely big production and fleet bonuses. Maybe they should be toned down a bit - don't feel complete comfortable with a 100% damage bonus just because your fleet has a good commander .