Whenever I try a one-of, I seem to end up using it to make a crocolisk painlessly remove a sarge or something. That's just where the use case seems to wind up for me..
I've never seen it used at a high level, don't see it pop up when I get in the 1-5 ranks, so yeah, it seems to pretty unanimously get considered unplayable. It's a lot like Giant Growth from magic, the maximum possible value is really really high, but having both a friendly minion and an enemy minion and a way to make sure they fight eachother while you have the mana to spare ends up being too many hoops, usually.
If you use it to rescue 1/1's, it sometimes gets considered less of a value play because any /1 is in the "swipe debris" status where mortal coil, swipe, and fan can all get really high value in the process of clearing it out. It's the reason Commanding Shout is unplayable or incredibly close to it, even though it's a cheap cantrip that can save three creatures, swipe debris is swipe debris