1) Maybe we should leave everything as it is? In the sense that there are currently heroes who are strong at specific stages of the game and on specific maps, and, in principle, I don't see anything wrong with that. And the fact that the chosen map and the player's strategy narrow down the number of heroes they will start with is quite normal; this isn't an MMORPG where each class should always be balanced relative to the others, as the character is developed over months.
2) Or, clearly divide the heroes into "early-game," "mid-game," and "late-game" heroes and try to balance them within each of these groups so that, for example, early-game heroes are strong in the first 2-4 weeks, and then their effectiveness decreases, but they can still stay afloat thanks to the advantage they have gained; mid-game heroes are not so strong at the beginning, but after developing the right skills and abilities during the first month, they are able to show their maximum potential during the second month; and late-game heroes start to heat up towards the end of the first month, at the beginning of the second, and the longer the game lasts, the stronger they become. Something like that; this is just an example, a more abstract division would be even better.

This is really useful! Thank you!