gruul aggro post rotation help

First off, if you're R/G (aka Gruul), why do you have Temple Gardens?  A normal mountain would be more effective in casting Boros Reckoner as it will never enter the field tapped and can be used to cast it.  You don't have any other white in the deck...

Second, you have nothing to actually drop with Burning-Tree Emissary other than another BTE or perhaps your one-drops.  You need to have some two drops to give you options.

Third, I don't know that I'd run Purphoros or Domri as 4x.  Not only would this require you to obtain 4x Purphoros (who is pre-ordering at like $25), but they're legendary - making ANY duplicates of either in your hand dead cards.  I could see Domri as 3x at the most and Purphoros perhaps as a 2x or MAYBE a 3x.

Fourth, I don't know that I'd run Madcap Skills in here.  Sure, it works wonders in sealed and is a monster card in the right instances, but given the small size of the creatures you're using, it's inviting you to get two-for-one'd a LOT.  Think, you put it on a BTE, they hit it with Magma Jet.  Now you're out two cards to their one.

I'd actually suggest looking at Craig Wescoe's list and then see what changes here or there that you want to make it more your flavor.  You can see his article here: http://magic.tcgplayer.com/db/article.asp?ID=11358

For cards you're leaving out from Theros, simply put, go look at Reverent Hunter, Satyr Hedonist, and Xenagos (although I'm thinking he'll be best for a more mid-rangey deck).