Blues sometimes being better than yellows is fine and intended. It's when they end up being superior to legendaries (from the same difficulty level), that I take issue with. Legendaries are undertuned.
If it's anythig like D2, blue vs yellow vs legend only has to do with how many different stats the item can have. The individual stats can be random so the same stat can be higher on a blue vs yellow / legend. That's why if you ever get a legend with the correct stat, it would be uber compare to blue or yellow. That's where loot farming kicks in.