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If the map (or save file) from the generation is still available, you can check to see if all the native heroes ended up in prisons.
In a normal situation, this doesn't happen in Haven; heroes of each class stop ending up in prisons when there are too few of them left. But on the mirror map, after the main generation, additional prisons are added on the other surface (with the same heroes), and at that point, there might not be enough of them. That is, if 7 prisons with Tower heroes were created on one plane, there will be another 7 Tower heroes in prisons on the other plane + 2 starting heroes – and there simply won't be any heroes left for the tavern.
Without using the Wizard, this is difficult to fix, but you can try.
If the problem isn't with the prisons, it would be helpful to have the map seed (listed in its description) and a description of the generation settings (template, starting cities/heroes for players, etc.). Then I can reproduce the generation and figure out why these particular heroes are appearing.