It all depends on whether there is a limit on the maximum number of units that a stack of Mighty Gorgons can defeat... The maximum number is equal to

D(max)=N/10+1, where N is the number of Gorgons in the stack (rounded down to the nearest whole number).

The most effective division in the example above would be: 1+1+1+1+1+1+16.
The first stack takes the initial hit, and the rest attack without losses. The maximum possible (additional) damage in this case would be 8 enemy units in the first round of combat, 6 in the second, 4 in the third, and 2 in the fourth... A total of 20 units in the end (if you're very lucky, of course :) )... But what if the opponent had Azure Dragons? :)

All that remains is to compare the probabilities :)

Added 9 minutes later
I'll risk copying another assumption

"I present to your court the 'final solution to the Mordor problem' (c), or What we know about Wyverns.

Let's start with the official data. The game's reference states:

Wyverns and wyvern monarchs attack with swipes of their stinging tails. The wyvern monarch’s stinger has a chance of poisoning its target for three rounds. The top creature of a poisoned troop loses 50% of its health each round. Poisoning can only be removed by the Cure spell.

In the Bukowski translation, this means that

Wyverns and wyvern monarchs sting their opponents with their sharp tails. The poisonous stinger of a wyvern monarch can poison the victim for 3 turns. The first creature in the poisoned stack loses 50% of its health each turn. Such a stack can only be cured with the Cure spell.

As one well-known person said, 'this is once again a case of so-called lies.'

What does practice show? And here it is.
Let's conduct a simple experiment. Hotsit, 2 heroes with 0 attack, all other parameters at 99, and knowing all the spells. One has 7 stacks of 1 upgraded wyvern each, and the other has 4000 pikemen. So, we slowly attack them, poison them, revive them, heal them... in general, we experiment. The result is as follows.

Poisoning is applied with a probability of 20% and lasts for 3 rounds. Each turn, it removes 10 percent of the maximum number of hit points of all creatures in this stack + it also poisons one creature in this stack for 10% of its maximum health. At the end of the poisoning, the stack has 70% health remaining forever, until this is removed by healing. Re-poisoning the same stack will result in another 20% reduction in the 'total hit points' over 2 turns and + damage to one creature for 10% of its maximum health for all 3 rounds. Further attempts to poison do not lead to disastrous results for the entire stack, but only affect 1 unit.

Notes:
- A creature that is already poisoned and has the spell active is immune to further poisoning.
- Some creatures cannot be poisoned (I can't compile a list of all such creatures)
- When attacking unicorns, the probability of poisoning them is less than 20% (IMO, I got something like 14-15 out of 100)
- The presence of any expert magic and/or sorcery in the hero does not affect the effect of the poison
- The healing is true - poisoning is not removed by dispel or anything else.
- Added. Check if the resistance skill affects the probability of poisoning.

So, there are no 50% here and there can't be in principle."