KMST 1.2.410 - Skill Changes

I don't believe that the actual KP use values were removed from the skills, just the descriptions. At least, going by what Fiel posted.

There are quite a few skills that have values attached to them that aren't used I believe, especially the new, unfinished ones. If other skills use KP, then this system is completely worthless as the only skills you have to charge KP are basic attack, Double Stab, Savage Blow, and Steal.

Mmm, by what you are saying and the fact that Shadow Instinct only lasts up to one minute now, does this mean that we only have up to 60 seconds to charge up Assassinate?
This would explain the low duration time of Shadower Instinct I suppose, although I still think 60 seconds is a very low duration regardless of the Killing Point success rate, which as you said is unknown. Would the extra attack of Shadower Instinct be calculated at the moment of casting or does it change every time you get a new kp. If the extra attack is calculated each time a kp is gained or used, then every time we use Assassinate and it brings the kp back to 0, our attack would automatically decrease, so it would be better to use it right before the 60 seconds are up I suppose.
My guess is that you don't know the answer to this but it doesn't hurt to ask so, do the Killing Points go away after each Assassinate?

You get the attack when you cast the skill.