muckypup1
Sinister Haven \m/
I would really start learning stuff that is not so technically challenging.
Good places to start are
Slayer
Megadeth
old Metallica
Anthrax
Those guys were the king of downpicking and rhythmical complexity back in the day. From there move onto things like Fear Factory and Meshuggah to really push your right hand. From there move into the stuff you were talking about earlier.
You need to learn to walk before you run. A shit ton of the students I teach come in with all this technically challenging music and they barely have the right hand to pull of an Iron Maiden tune ..lol
In addition get a metronome and play with it furiously sub-dividing the beat in every way possible. 1/4, 1/8, 1/16, 1/32, then all the dotted versions of them. Learn to count and learn Time Signatures.
All the theory in the world doesn't do anything if you lack the technique to play what you hear in your head. Technique takes TONS of practice. Its a cunt to stay disciplined enough to do it, but in the end its worth it.
Those are still pretty hard bands to play like... Everything from Reign In Blood just makes me when i try to play it