Apologies for late reply.

On the first effect. I was basing it off an effect i'd seen in several other classes. It's possible i've either misunderstood what it does in those cases or badly worded it. The idea was that you'd get this as an additional add on top of normal proficiency effects.

On Assassin Strike. Raising the Floor was very much the point. That said i genuinely wasn't sure where the line was on that. How would changing the 17th level effect to an on critical only, (possibly with, possibly without), a critical range increase?

Masterful Infiltrator may again be a flaw in my understanding of the hiding rules. But as written you can't hide successfully in a fight as once someones aware of you, you can't just drop into hiding. The main thing i was trying to do though was give you enough duration/uses to infiltrate a guarded compound, take out your target, then sneak back out. Since killing your target would break normal invisibility, (and i really didn't like the idea of handing out greater invisibility of any great length), that meant more than one use would be required, and infiltrating a compound might require even with invisibility setting up distractions and waiting on patrol's, which would mean more than one use to get in or out and a fair amount of time. I'm open to ideas on how to achieve the effect without breaking things.