You may want to use heavy attack why? It because this levels up Coldblood.This skill can be leveled up by killing enemies with a bladed melee weapon's heavy attack (has a special kill animation
The Cold Blood skill focuses on improving V's basic stats and defenses such as Armor, HP, and Stamina, also features critical damage, Resistance, and movement speed which is need for this build.
Best weapon for this build is the Katana satori which is in the heist mission. 500% critical damage, and with the right perks you could get over 100% critical rates.
As of this patch 1.04 If you have missed the weapon you could no clip the way up receive the weapon
I tried to get the weapon by this method. it worked for me, but it took a long time also made a lot do saves to do it.