Originally Posted by
Jesture
You've got two different things going on here.
The first is your general dislike of the card. I'm not sure what to say here other than you'll almost always have a use for Stifle. Between fetchlands, planeswalkers, wastelands, deathrite, miracle triggers, equipment (jitte, sofi, bskull, lightning greaves), lavamancer, delver flip, ports, pfire, vial, etb triggers (stoneforge, craterhoof, ringleader, snapcaster) emrakul, griselbrand, sneak attack, and various others I'm forgetting, you should be able to find a use for a single copy of stifle in most matchups.
The second is your dislike for one-of cards. I'll point to Become Immense, Crop Rotation, and the recently removed Dig Through Time as examples of singletons that are considered optimal in deck construction. The inclusion as a one-of shouldn't be a problem if you feel the card does not have a place in the deck, as this can be solved by simply not playing the Stifle.