In Diablo your hit% is an example. What happens in code is it first randomly generates a number from 0-100. Then if that number is below your hit% number it's a hit, if it's above, then you miss. That is a 5D20 roll. Then each weapon has a range of damage, say it has 1-10 damage. That means the program does another 5D20 roll, then multiplies it by the range(10) and the roll/100. Then it most likely rounds the outcome to the nearest whole number. That's the damage it inflicts on the enemy. This occurs every swing, cast, and enemy swing, cast.
How do you think the levels are created? Random generation! Including loot, enemies, item placements, shrines, chests, even quests! Diablo is a prime example of D20 in games.
The game is based around stats. Each stat effects a certain element of your character, that's D20 logic right there.
As for two human, never played or heard of it, so I couldn't tell yah.