I'm having a bitch of a time trying to nail this quick time event. And in the event that I do start it, it'll usually glitch with him jumping past me and not trigger the second button in the sequence. Is it even worth trying to hidden blade the thing, or am I better off just letting Myriam shoot the bastard?

She shoots him even if you get both buttons. 

Well that seems... like an entirely unnecessary sequence then. I also, not shockingly, just managed to get it. It had apparently continued to hitch up on the second press and count it immediately as in incorrect/too late prompt as soon as it came up. I thought the timing was just tight so you'd have difficulty collecting the prize, but when it worked right, there was ample time.

Bummer.