Still a no-recoil STAB Head Smash from Rhydon would kill.
Actually ZeroTarken is right in pumping up the Sp Def first.
X-Act's Optimal Defensive EV Spread
I checked the box 'Has Soul Dew' to mimic Sandstream and set both defense modifiers to +1 to account for Eviolite. The result is 252 EVs in Sp Def to be most efficient for an EV bias towards Special Defense > 71%. Even with equal bias between defense and special defense, it recommends 72 HP / 180 SDef, not max HP.
And this is with Careful nature (if it was Adamant - it would suggest more EVs into Special Defense).
EDIT: Oops, Rhyperior is still UU.