I couldn't find the exact blade he's using, but this is kinda close.
His blade is closer to a needle with a hilt, and he can only use it the way he does because he is naturally faster than humans. No matter how fast his target is, he's always faster. Holding the blade the way he does, and by it's design, the tip would sink through the flesh like a hot knife through butter, so even if your guy managed to move, he would need only an instant to sink it in, adjusting for the movement of the body beneath him. But since he would feel the move coming because of how he's positioned over all his major upper body muscles, he'd have plenty of time to push down the 2 inches he'd need to pierce the place he's aiming for.
Heheh, I too do much killing in games, but I also do a lot of anatomy and weapons research outside the gaming world. That coupled with my understanding of the Fae Assassin I've made and his training and reflexes, having him tossed off with my calculations on the matter seems impossible in my head. With the tip already against the skin, any movement would make it's needle like point sink in.
I kinda went over all this in my sleep, and I did come to the conclusion that the weapon description I gave wasn't enough to accurately represent how he goes about killing. I also concluded that this may very well have been a perfect occurrence of a bad ass battle. In other words, you wanted your guy to look cool, and I wanted the same thing and the math of your tossing made no sense to me, so my ego got bruised when you tossed my guy off, and you thought it would look so kool to do it that way so you did it :P
In other words, I'm sorry to make it sound like my character is better than yours, if that's the impression you got.
Oh, and it wasn't what yer prince was thinking that made him sound foolish. :P I understand him totally about all the failed attempts and "Ugh, not another one!" Heheheheh.