Nice sense of motion with underlying composition: dagger to the left, gun combined with hair locks and ear\(shoulderpad blade?) duo create a fit eye-guiding direction network, thusly 5 for vision.
Originality? There aren't a whole lot of alike group scenes I've seen here, though the idea doesn't seem to be new. Well, anything can be captivating with adequate workflow (:
Technique? I'm sure the picture could use a little bit more of rendering, although in my opinion what you've posted is already a nice example of full-blown style, so 4/5 from my perfectionism to your perfectionism (% I think adding more shadows to their faces (defining muscles!) would help developing the characters' feelings expression, as well as personalities show-off. Yes, this is what I'd do.
What's impact? Impression, I assume. Uhm... 4/5 as well, due to perfectionism.