enemy heroes

[BB Shockwave]

Much agreed.

Frankly, as for the mana, you can do that yourself by messing around in the Sessions. And I will probably do it, too. It's ridiculous for a non-mage enemy with 1-2 Intellect to have 100 Mana. Sadly, this was a common trend in AP too - it was the developer's method of making even measly pirate captains a challenging fight. All it
did for me though, was making no-loss harder as even one Poison cloud every turn is quite a big danger.

As for your question about the Necromancer's odd extra "buffs" - yes, he gets bonuses - the terrain where you fight him is considered a cemetery, ergo his Undead troops get +1 Morale. Add to that that Plague also increases undead Morale (I think...) and this could be explained.