This. Considering Heracross has roughly the same power as Nidoking and has the exact same Speed, and he's a bad choice for a Choice Scarf, I would advise against it. Not to mention there are far better special tanks and walls than physical, which means Nidoking has an even harder time running a Scarf.The Scarf sets, IMO, miss out on the extra LO boost. Plus there's always the problem of getting locked into a move.
If you're going to use a Choice Scarf on Nidoking, you're using him for the wrong reasons. Roserade would make a better Choice Scarfer for the same reasons you listed. It's harder to predict, since most Roserade's in OU are TS or Spikes based, so running either of those moves on a Choice set can mess with foes late game. Also has Sleep Powder. It even doubles as a status absorber.
I really, really wish Nidoking was better. It would need, at minimum, base 100 Speed if it were to function in OU. It is, however, a godsend for Poison-type mono teams when teamed up with Venomoth. That's about it.