1. No. It's not like Heroes 3.
2. A good primary tank (preferably 600+ HP), a good secondary tank (paladins will do if you can get a hold of them), and 3 ranged units - Archmagi, Inquisitors and something else.
3. To be honest... try to kite some map guards away from the maps. It takes some practice, but it's doable. Otherwise... restart the game on normal difficulty.
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