Tactics Lore - indirectly, it increases weapon damage and critical chance, thus making Ruthless Mutilation hit harder, also increases Life Leech damage from the Dolor mod and allows modification points.
Any weapon lore (such as Sword Weapons when the Inquisitor is wielding a sword) - will indirectly increase this combat art's execution speed, damage and chance to hit, and will allow the equippng of higher level weapons used to execute this combat art.
Combat Discipline will increase its Damage and reduce its regeneration time if this Combat Art is placed within a combo. This increase in Damage is direct; it increases the +xx% that the CA adds to base damage.
Speed Lore - will increase its chance to hit indirectly by increasing a player's attack rating.
Up against enemy crowds, the Inquisitor can use this to "mow" through his enemies, effectively giving him the ability to kill numerous foes in one attack.
When using the skill Dual Wield, the Inquisitor will make two half-circle weapon attacks (one with each weapon).
As with his other core weapon attack, Callous Execution, this combat art also has an inherently low regeneration time.
If the Inquisitor needs to get away from the enemy crowd he is facing, he can use this to slow them down and thus give him some time to back away from them and recuperate.
Combining Ruthless Mutilation with effects that instill fear in enemies will turn the Inquisitor's foes into slow moving, easy sacrifices for Ker!
Interestingly enough, this skill also works with long ranged weapons:
If the Inquisitor executes Ruthless Mutilation while holding such a weapon, he will shoot off 3 projectiles at foes in front of him. In the unpatched game this was much more powerful, shooting off one for each foe in front of him.
Also, the speed reduction is cumulative and it applies even if you do not actually do damage to the enemy. With a ranged weapon, Deprivation mod and reasonably low regen time you can quickly reduce enemy movement speed to a crawl.
Effective with either (or both, if using Combat Discipline): Callous Execution and Mortifying Pillory.
Also performs well with Levin Array; the Inquisitor can slow down his enemies with this and then fry them with lightning.