P.S.S ACUITY is nigh useless; the numbers need tweaking. Even late-game, even with critical hits as a focus, you barely get a (on average, deviations notwithstanding) 1.1-1.2x damage multiplier while if you just put more of the points into the main scaling stat you'd get easily a ~1.3x (on average, some upgrades are better for combat rather than events than others) multiplier with practically a third or fourth of the cost.
It is not even good as a spill-over stat because spending those points on any other combat skill is more effective for sustain or AP management (not including DEXTERITY for non-DEX builds).