End of Mystery...
Feral Druid goals: Hit cap: 295, Expertise rating: 26-30, Crit: at least 50 percent. Gem Strength, don't bother with armor penetration.
Okay.. more on that...
If you depend no your rip for dps, it is affected by attack power, and not armor pen. If you switch your dps more in favor of Melee hits and Ferocious bite, armor pen helps a lot. If you go for the 4 piece T8 set bonus, it increases Savage Roar, and you can fit in more Shreds and FBs, and stacking armor pen would benefit this dps.
Link to information:
Then again... here is an opposing view!