Gen 5 Tiers are not sorted/created so comparing it to Darkrai is not a horriable thing to do
Personally I think Substitute is worth a look since otherwise priority will stop any attempts at a sweep.
EDIT Half my post got Ninjaed by Knight
EDIT 2 at ChouToshio
Could you not argue that Infernape could run SD and NP sets well?
Certainly I would imagine it got more use than SD Scizor