Your hi's are a bit overpowering, your secondary and bass are a bit shadowed by the lead.
Your snare has a bit of fluctuation that is heavily noticed through a iPhone's beautiful surround sound speakers...then there's the sound system I use through-out my house, and you can clearly tell everything above.
Your cover is spot on and has a nifty unique touch, but I'd take a look at your mastering one more time and touch up the volume in sections and even go a bit more..."violent" with your bass and secondary in certain areas to give it more of a natural feel, and reign true as an epic cover.