stop... stop... stop!
This map requires a lot of heroes. I might not even know who among them were escaped/killed and who weren't!!! Okay, let's do this: I simply won't transfer artifacts. Because what difference does it make? I use them to move around the map... it's very important to avoid problems later.
And how to determine if a hero is used or not - I'll tell you...
1. A new hero always has less than 100 experience points.
2. An empty spellbook for the Sorceress and the Wizard... the Barbarian and the Knight don't have one at all.
3. No artifacts and no additional parameters.
There's a 1-5% chance that the computer might have discarded a hero - while leaving him "clean" in all 3 points.