I would definitely use different drum samples, especially the kick and snare. They sound a little too machine-like at the moment.
I'm not sure if it's a mastering issue, but there it sounds like there's a bit too much high end overall, particularly in the rhythm guitars and drums. The hi-hat sounds really tinny and thin.
Try bringing the bass up a little bit, and maybe bringing out more of the low end.
The clean vocals sound like they need some work in Melodyne. A lot of the notes aren't quite where they need to be. Sounds like the doubles could be lined up a little more tightly. Lastly, I think the clean vocals need a little more reverb or delay to sit better in the mix.