The Chess event of Karazhan was designed for a raid of 10 people during Burning Crusade. It was more or less a prototype vehicle fight like those introduced during Wrath of the Lich King. Those fights eventually received scaling based off the player's item level and with the help of equipment from later expansions, players became able to solo these fights.
As far as I can tell, the Chess event doesn't scale: the pieces' health, damage and cooldowns are fixed. Despite this, I can easily defeat the event on my own by controlling the Conjurer/Warlock and nothing else. Even before I perfected my strategy, my NPC pieces usually managed to kill the entire enemy board And I could defeat the enemy king without losing mine.
Did the mechanics of the Chess event change at some point? Were the other 9 players always this redundant?