That shell is pretty good, in my opinion all lists should have 3X Dread Return and 4X Ichorid, which leaves 3 slots open, which I fill with a 4th Mine and 2 Gamble. I suppose if those last 3 spots were something that didnt cost mana like Street Wraith or Leyline you may be ok with 7 rainbow lands, but Id rather be able to cast Gamble and my SB cards more reliably.

