Everyone that says Feral PvE isn't even a thing in Vanilla obviously has no idea what they're talking about. There are a small handful of Feral raiders on Vanilla private servers that not only do well enough to justify their raid spot, but they can even beat out every other DPS on certain fights.
They require a MUCH different playstyle to accomplish this, however. The playstyle revolves around using the
Wolfshead Helm , a level 40 helm that allows you to generate 20 energy when shifting into Cat Form. With this and 5 points in
Furor , you will always have 60 energy when you first enter Cat Form. Then, you basically shift in-and-out of cat form quickly when your energy bar is depleted, allowing you to maintain a DPS rotation that isn't at all possible without this "powershifting" method.
That's the only way to do it in PvE, however. If you play the spec any other way, then you absolutely will not deal enough damage to be brought along to anything and be worth your spot. But it IS POSSIBLE to really compete as Feral DPS.