ToME: the Tales of Maj'Eyal

Other tier lists consider things like 'ease of use' or 'power'.
This one is just the numbers.

S-Tier
These classes win an outstanding 5% of the time. They need to be stopped.
Sawbutcher
Temporal Warden

A Tier
These classes win an impressive 3% of the time
Summoner
Mindslayer
Doombringer
Skirmisher
Oozemancer

B-Tier
B-tier contains a wide range of power, but no notable gaps.
B+
Possessor
Shadowblade
Demonologist
B
Paradox Mage
Stone Warden
Berserker
Wyrmic
Bulwark
Psyshot
Solipsist
Reaver
Cultist
B-
Sun Paladin
Cursed
Brawler

C Tier
These classes win about 1% of the time and are perfectly fine
Gunslinger
Archer
Writhing One
Alchemist
Rogue
Arcane Blade
Necromancer

D Tier
These classes are not even close to winning 1% of the time. Perhaps they lure you into making bad decisions.
Anorithil
Archmage

F Tier
These classes, for whatever reason, win less than half a percent of the time. Please help them.
Marauder
Corruptor
Doomed

The only consideration for a class is how often it wins Insane/Madness, based on the public character vault. With only official addons
Roguelike and Adventure together
Maj'Eyal campaign only

what do you mean by "win 5% of the time"?
is that "among all i.e. sawbutcher characters on insane/madness difficulty of game version 1.5.10, 5% of them are winners"?