Heroes 5.5 WarGame Edition - Tactical Edition.

I would never have invested in a perk that harms an army... killing three neutrals and losing 15% of your army?

First, this penalty has already been removed (Battle Frenzy has become a level 2 perk).
Second, the number of troops here is much lower; losing 5% at different stages of the game would only affect tiers 1, 1-2, or 1-3. That is, due to rounding down, it wouldn't actually be 15% of the army after 3 battles.

So, personally, I don't see any balance issues here, but I still removed this penalty so that players wouldn't be afraid to use the basic level 1 perk, fearing a negative outcome. And in a truly long game (more than a month), such a penalty would indeed have a negative impact.

Similarly, I reviewed and adjusted the troop recruitment skill so that there wouldn't be an overpowered situation in a hypothetical very long game (and it wouldn't be possible to get significant bonuses from roaches bringing in large troops). Also, as with diplomacy (a gold limit for ransom has been added, depending on the hero's level - the idea was taken from Heroes 4). Previously, troop recruitment gave +5% troops per day (with the same rounding down), now it gives a fixed number of creatures upon reaching levels 3, 6, 9, etc. of the hero, and it doesn't work at all for roaches of levels 1-2.

That is, the logic is as follows: a low-level roach should not receive strong non-combat bonuses from skills. And weak skills are not needed for combat heroes. Hence, the link of such skills to the level.

Added 21 hours 41 minutes ago
Regarding racial skills (still in development):

DEMONOLOGY
1) Quick Gate -> Wide Gate / Fortunate Gate
2) Hellfire -> Blazing Flame
3) Corpse Eater

Fiery Retribution has been removed (immediately integrated into Hellfire).
Exploding Corpses have been removed (immediately integrated into Corpse Eater).
Curse Mark has been moved to Occultism (Dark Elf racial skill).

RUNES
1) Attacking Seer -> Rune Harmony
2) Defensive Seer -> Rune Recall
3) Economical Rune -> Refreshed Rune

Double Rune (Greatest) is questionable, as it is incredibly strong in the late game (like in Castle?).
Therefore, it is questionable what Special Ability (SA) the Dwarf will have left, Double Rune or Absolute Protection.

AVENGER
1) Enchanted Arrow -> Enchanted Ballista
2) Deadly Shot -> Rain of Arrows
3) Native Lands -> Sudden Attack

Forest Trickery has been removed (completely useless, doesn't scale).
Forest Fury has been removed (can be integrated into Talanar's specialization with Fury).
Forest Leader has been removed.

COUNTERSTRIKE
1) Double Strike (Devil's Strike with 100% chance) -> Vigilance
2) Prayer -> Twilight
3) Warlord -> Mentorship

Warlord automatically trains (increases) creatures depending on the level of the Counterstrike hero: 3 militia / 2 archers / 2 swordsmen / 1 monk for each hero level (including those already obtained).

RAGE
Blood Memory -> Battle Frenzy / Fury of Fire
Reinforcements -> Stun Blow
Goblin Aid

OCCULTISM
Killer's Mark (Curse Mark) -> Torturing Strike
Dark Ritual -> Fallen Knight (will be renamed)
Enhanced Magic (Arcane Wave) -> Elemental Sense

NECROMANCY
Banshee's Wail -> Deadly Misfortune (-1 initiative against the enemy hero)
Eternal Slavery -> Master of the Dead (+mummies) / Herald of Death (+death knights)
Spiritual Bond

ARTIFACTS
Magic Mirror
Wizard's Sign
Artifact Absorption -> March of the Golems / Machine Loyalty