Unit 1 was designed for a peak ground acceleration of 0.18 g (1.74 m/s2) and a response spectrum based on the 1952 Kern County earthquake. The design basis for Units 3 and 6 were 0.45 g (4.41 m/s2) and 0.46 g (4.48 m/s2) respectively. All units were inspected after the 1978 Miyagi earthquake when the ground acceleration was 0.125 g (1.22 m/s2) for 30 seconds, but no damage to the critical parts of the reactor was discovered. The design basis for tsunamis was 5.7 meters.
So they modeled off a specific earthquake. But people certainly knew it was possible that a larger earthquake could happen. The probability of operational error for the plant was on the order of 10^4 or 10^5 and this thing was in operation for about 10^5 hours.
Problem is, how do you make it 'difficult' without being 'grindy' outside of PvP, and still making it attainable for everyone with the dedication.
The WoW game at it's heart is simply too easy. It's intentionally set up so that clever tactics can't be used (simple physics, fake terrain, non-existent line of sight rules, etc.) and the longer it lives the more it just becomes about cycling through hotkeys.
Fundamentally, there may be no basis for anything.