Or to take the Judge, Soul Hunter or Vigilante archetype if you're dipping into stalker and would prefer to not boost Wis.
But IME, a stalker rarely needs deadly strike to last more than one round when triggered by a crit as per default, and could thanks to some related Stalker Arts probably get tons out deadly strike even without a positive Wis mod. Which I guess is also partly why deadly strike wasn't given the typical "minimum 1" clause.