I thought your work was poorly inked, I didn't realize it was pencils. I'd suggest not darkening the stuff. Make sure it's clear that what you're showing is PENCILS.
I actually find it hard to believe that an editor *actually* thought you were submitting a writing sample. I'd be inclined to think he was trying to teach you something about submitting art samples while also attempting to diffuse any personal offense on your part by talking about "your artist" rather than "you". Kind of brilliant, actually.
I will say that the excellent Cap face on page one shows you have the talent to get there with more work (and the half-assed muzzle flares on Natasha's guns on page two show how far you still have to go...)
Seriously, it appears to me that you're at that almost-there stage where you just need to keep drawing until you have that breakthrough. I've seen it happen REALLY fast for some people at your stage. It really just comes down to how well you can see your own weaknesses at this point. If you're delusional, you'll never break through that wall. If you're honest with yourself, it's only a matter of time.