You know that defensive Rapid Spin alternative EV spread listed in AC? The one that goes 252 HP / 80 Atk / 176 Def? That's actually Donphan's best EV spread. Personally, I use 248 HP / 80 Atk / 176 Def / 4 Spd to always outspeed Chanseys (that aren't speed creeping), whom Donphan dislikes.
Oh yeah, and offensive Rapid Spin is really awful and should not be getting a set in this analysis. Trust me, I used to use it extensively back in my noob days, and oh god was it terrible.