Heroes 5.5 WarGame Edition - Tactical Edition.

Leadership skills are too overpowered, almost all of them. I wouldn't recommend dealing with complex percentages at all. Tested. (and there, +5% was awarded per week, but here it's per day).

Arcane Luck: The hero's spells deal an additional +50% damage with a 10% chance for each point of luck.

Cool. It was already difficult for a Warlock to win in the late game against someone with their focus on destruction, and now they've cut his damage by another 50%...

Fireproof Armor: The hero receives +2 to defense. The hero's units receive 50% less damage from the Fire element and are immune to the "Fire Master" ability.

There are already abilities that provide protection from fire. For example, in the light branch. At the same time, other elements are somehow ignored.