I used Feint once while leveling up in 2004. I was in Razorfen Kraul, attempting to duo Agathelos the Raging for a shot at a Swinetusk Shank. While fighting Agathelos, the great boar focused on me. With Evasion down, my life was dwindling. My brother of the shadows told me to use Feint, which would lower my threat. It didn't reduce my threat by enough, and I died. I learned then and there that Feint was not my friend. Luckily there was a dagger on the boar's corpse, so my run back was ever so sweet.
After Tricks of the Trade and Misdirection entered the scene, I put Feint on button without a hotkey -- the action bar equivalent of Siberia. For nearly five years, Feint went unused. Rogues already have potent passive threat reduction. Patch 3.0.8 changed all that, and now I'm pressing Feint as often as Mutilate or Envenom. Feint is now a core ability of the rogue class.