Evisceration:
Mercy Stroke (Sneak Attack):
Mercy Stroke (Unstacked):
Upgrades:
Coruscanti would be a better offhand.
Toci's Harness (13 STR, 13 DEX, 10 Accuracy, 10 Attack, 3% 2A) would be an upgrade on both Mercy sets, and probably on Evisceration in no Atma situations.
Whirlwind Dirs (12 STR, 3% 2A) would be an upgrade on unstacked Mercy. Sneak Attack would depend on the mob's defense.
(Hecatomb Leggings have STR and Attack augment. Subligar has STR, DEX, and Crit Rate.)