The high note hits in the beginning were too high, maybe you could lower them an octave.
This isn't "Dubstep" in my opinion, it is D&B.
You got 4 stars from me, because this is just simply isn't dubstep. if you would have rated it as D&B, it would have gotten 5/5 easy :) ( I actually rated you 5* )
As Varsity mentioned, a riser would fill the awkward gap you have in there right now.
Even if you don't have any "risers" downloaded, you can be creative, and make your own: A lot of attack + release, and slowly *and exponentially* increasing the pitch of the instrument makes a nice riser (with a little practice).
I have found that you can make dubstep without purchasing anything, you just have to be creative, and be willing to put work into it.
To make "wubs" you just have to use a bass, and change the pitch quickly. voila. with a little practice, (and in the correct atmosphere) this can sound amazing!
Overall, this is an amazing piece, which could be taken to another level, with just a few minor changes!