scars of reality, 4000 mana rounds are enough. All we need in this scenario is to recast Hypnosis on two stacks of Liches and Antimagic on a Harpy every hundred rounds. Bloodlust and Executioner are not needed, as the same effect is achieved by using Devastating Ray more often.
But the battle, as intended by the author, isn't that sadistic, and as far as I remember, it was originally planned so that any alternative tactics, if discovered, would look absurd.
In general, the proposed solutions for the battles are very good, especially against a combination of heroes with Rusty Dragons. Victory with virtually zero mana expenditure in the second battle! And who would have thought that the original ways to complete it were different?
If anyone wants to share their walkthroughs of the battles and not only on these maps, I'd be happy to see them.