Mobility classes are most of the time stronger when everyone is still learning the fights.
the strong showing of the few ferals will close over time probably... as other classes learn to have more uptime and optimize around boss abilities. It is easier for cat to run in/out and you have a lot of energy pooling inactive time where you can deal more easily with running around. But i also expect a bigger benefit from other classes legendaries... i am underwhelmed by the overall affect of them for a feral compared to not wearing one.
If you wear 10 ilvl lesser gear compared to feral with leg., balance will sim 500dps higher without wearing a legendary...