NHF – new heroes for Heroes V 3.1.

It's not really fair to simply reduce half of any stack, regardless of its size, with only a 25% chance, without checking the ratio of parameters.
We give a weak hero a Random Skill, divide it into several stacks, and we get a chance of at least halving the stack once: 44% for two stacks, 58% for three stacks, 68% for four stacks.
If the ability worked with a standard check, I wouldn't have any complaints about it. :)

Using the same logic, one could argue that a single caster unit is overpowered. It's "not really fair" when 1 monk casts a buff on 10 angels. Or when 1 paladin removes mind control. Or when 1 single peasant unit removes retaliation or blocks the passage for a crowd of knights. And so on. There are things that play a role in certain situations, regardless of the amount of units, and this is a perfectly normal phenomenon, in my opinion. The fact that they are supposedly imbalanced has not been proven by anyone yet. Some people simply like this state of affairs, while others don't.

As far as I remember, the Random Skill doesn't have a speed of 8, and it doesn't turn corpses into retaliation units, so the chances of actually hitting anyone in the aforementioned scenario are quite slim. If we're talking about breaking through, then it won't be possible to break through for a long time in this way, unless with cheat loads. And even then, the effect of halving is questionable, because if there are few Random Skill units, they won't be enough to finish off even the halved stacks. Moreover, when attacking sufficiently strong neutrals, there will be many stacks.

In short, in my opinion, the overpoweredness of this ability is a myth.