Absolute skills

By the time any race has a Special Ability, Humans will have so many trained Paladins that neither constant luck, nor super defense, nor -6 to morale, nor anything else will help... this is done for balance... it's okay...

No doubt, Haven is very strong even without a Special Ability. However, note that it became so strong after the "reds" appeared in its ranks! Haven was cool before, but not as much, and its Special Ability was terrible from the beginning. Further, regarding "a Special Ability won't help":
I won't argue about Stronghold, I haven't tried it, although I'm sure it will be a bloodbath.
Regarding Orcs - doubtful. At the second level of "Fury," they are VERY angry.
Demons - also doubtful. Paladins are cool, but there won't be enough of them to cope (without mana) with an army of demons that has instantly grown by 40% (at least).
Regarding Dwarves, I'll give a dubious but still valid example:
The last mission for Dwarves (Hammers of Fate), Veteran difficulty.
Accordingly, the economy is in a deep... uh... hole, Laslo appears (a real pain) in the middle of the second month, half of the troops have not been redeemed. Laslo is well-leveled and, by the way, he is leveled in a rather tricky way! For example, I was quite surprised to see purely dwarven enhancements in the stats that boost his troops - defensive shield and offensive shield (which added to his already considerable Attack and Defense, and it was very difficult to deal with the archers huddled in the corner, protected by "ironclad" Zealots).
The first time I played without a Special Ability and suffered heavy losses. Then, dissatisfied with the last level (the computer beat me up so badly:smile35:), I replayed the campaign with a Special Ability. In the second case, Laslo simply got DESTROYED without inflicting almost any losses on me, except for slightly damaging the Lava Dragons with a direct hero attack. So, don't underestimate the Dwarves' Special Ability!
As for the rest - Mages and Necromancers won't be helped much by a Special Ability, and for the Elves, the Special Ability is so good that it doesn't hinder development at all (especially if you play as Vashtai), I would take these skills anyway, so it will be a serious bonus in favor of the Elves.