The amount of lockers to open for some people in order to get a mythical is not reasonable. Apex Legends uses a good system to resolve drop chances of elss than 1%.
The solution is to force that per 500 opened lockers, you will get at least one mythical. The drop chance can be 1/500 and that’s fine, but we should be guaranteed to get one if we do happen to open 500 lockers searching. Same for every other rarity. If the drop chance is 1/200 for exotics, the algorithm should force you to get at least one every 200 lockers.