Concert photos are tough. First, you have to decide whether you want sharp shots, or whether you are trying to be artistic with your portrayal of the band, allowing motion blur to provide "movement" and dynamism to your shot. Here you have decided, for better or worse, to blur your subject. Now, since this is personal preference, I have no problem with it, but I shoot a lot of concerts, and I have to say the best investment you can make if you start doing this a lot it is a 50mm 1.8 lens. Why? Well, with a 50 1.8 you can decide whether you want sharp (opening up the aperture) or if you want to creatively blur (stop it down) for this kind of lighting. WIth the zoom you are using for this photo you are stuck with one kind of shot, unless you use a flash, and you should never use a flash because artists hate flashes all the time and available light just looks better anyway.
Although this shot is dynamic and has some "flow" my guess is you are creating a lot of blurry photos using that zoom combo in the kind of light you were shooting this show, and few were as clear as you liked.
My recommendation would be to try a 50 1.8 stopped down to about f/2.0 if you get another crack at this. Thanks for sharing.
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