AnotherMetalmix... Need help with mastering!

I´m not specialised in mastering but here´s something I would try:
-Sweep for resonating frequencies with narrow Q. I think in this mix there are some resonances in the lower mids and. I bet cutting at the right frequencies will give the final master some power and air.
-Use a couple instances of different compressors. One with slower attack/release settings, maybe a compressor in opto-mode. Maybe 3-4db of GR here with 1,5-2:1 ratio. Then use another compressor (non-opto) with relatively slow attack but fast attack (remember to adjust so the compressor works in time with the songs tempo). Use only 1-2db of GR here with 3-4:1 ratio.
-Try to add some of that expensive high end sparkle for example with an exciter. Antress Modern Exciter is good and free (http://antress.blogspot.com/). Be careful not to overdo it, it´s TOO EASY :D If this brings out nasty resonances try to find them by sweeping again with a narrow Q and cut appropriately.
-Use a limiter but if possible not a brickwall limiter. I´d prefer using a clipper-type limiter to make it loud enough without losing the transients. Maybe a brickwall limiter after the clipper just for safety to nail the peaks to -0.3 or -0.4

Hope this helps...as I said I´m not specialised in mastering but this is a starting point for most of my metal masterings :)