In the main book there are currently three classes with sneak attack. That is far too common. Each class should ideally have unique abilities to call their own. For the slayer, I am thinking of replacing sneak attack with surgical attack.
Surgical Attack: At 3rd level, if a slayer catches an opponent unable to defend itself effectively from her attack, she can strike a vital spot dealing the listed ability damage. The slayer’s attack deals ability damage anytime her target would be denied a Dexterity bonus to AC, or when the slayer flanks her target. This additional damage is 1 point at 3rd level, and increases by 1 point every 3 levels thereafter. Creatures struck by this attack may make a Fortitude save (DC 10 + 1/2 slayer’s level + the slayer’s Int modifier) for half damage (minimum 1 point).
Should the slayer score a critical hit with a surgical attack, this ability damage is not multiplied. Ranged attacks can count as sneak attacks only if the target is within 30 feet. The slayer can choose which ability to affect before she makes the attack. It is assumed unless stated otherwise that this attack is meant to kill and deals Con damage. If she wants to quickly disable spellcaster she will try to cause a concussion dealing Int or Wis damage, to weaken a strong combatant for capture she may hit nerve points and joints dealing Str or Dex damage, and to teach a foe a lesson about their station in the world leave scars or horrible wounds in the form of Cha damage.
The slayer must be able to see the target well enough to pick out a vital spot and must be able to reach such a spot. A slayer cannot use surgical attack while striking a creature that has concealment. Creatures immune to ability damage, critical hits, or precision damage are immune to surgical strikes.