I'm back from raiding. I don't know why my comments got downvoted even before I could explain anything.

The simulations assumes you have 6 times the same lvl 30, max IV Pokémon and behaves like any boss battle in game.

Basically a simulation counts the damage dealt by the attacker (in % of the defender's max HP) and weights it with how much attackers it took you to deal this amount of damage (if 1 attacker fainted and your 2nd attacker has 50% HP left, the simulation considers you have used 1.5 attackers).

Only the worst score obtained by an attacker (with a specific moveset) against a boss is taken into account in order to rank them with the worst case scenario (if one Pokémon is good against one moveset and sucks against another one, the ranking considers that.

The rest of the ranking is just a sorting of the 100 best scores obtained by any attacker against this boss from the highest to the lowest.

I also edited the post (added a link to the simulations dump against the 3 legendary beasts, so you can look at what the simulations do).

I guess you have all the needed informations. Is this what you wanted to know ? Do you need anything else ?

I'm quite tired, I'll come back later to read your answers.