Either the achievement has some other ambiguous not stated criteria, or Sadistic Game Design is currently bugged.
78.3 Got through first dungeon.
60.6 Was so great they solved the puzzle, and got Radiance. (Dunno how many used walktrough or streamers.)
56.4 Survived first city.
40.5 Managed to get through Drezen.
28.5 Reloaded enough times to get timing with column right.
16.6 Unlocked all unlockable mythic paths before choosing.
8.2 Finished whole story.
8.1 Got the toad.
7.2 Decided to finish the game on difficulty level Asian and choose demon.
5.6 Were decent on strategy map and got army management ranks to 5.
4.4 Only few people wanted to be a dragon.
3.5 Defeated Khorramzadeh's army on Strategy map. (Was that that weak army? Or that was just a appetizer?)
3.3 Saved cart of booze, and actor troupe.
0.9 Went with Swarm.
And then we have people who were rounded down to nearest 1/10 of percent, and they are represented as 0.0 percent. Hey, I Know You! is hard on blind ironman. (Random dice roll can screw that easily.)