Loot re-rolls don't always give you loot that is one class up. It re-rolls you into another loot table that could have loot that is one class up. The system consist of many loot tables that the Devs do not disclose.
For example: If you were to loot a Legendary item from an elite boss and Loot Re-roll was activated. What would happen? Would you loot a mythic?
Since this cannot happen, the game would re-roll you into another Legendary item and the system would have to randomly choose which of the two items would be your received loot. If that would be the case, then it would be safe to assume that this scenario could apply to other classes of items (common, green, epic)
Now I could be wrong, but this is just a theory.
Bookmarks