Looking at the list I spoted a couple of pretty basic issues.
First, you can't support cards that cost 5 or more with 20 lands and expect to cast them on curve. Even with ramp. Drop the 2 revel of the fallen god and put a lands in their place and also take out the defend the hearth and get a couple more lands in there and at least 1 more elvish mystic. That should give you 24 lands and 4 ramp cards. Keep in mind rootbound crag is not standard legal so if you went to an FNM or something you'd have to replace those with other lands.
This is a GR devotion list I have together. It's not the "ideal" list for these colors these days, but it does okay.
http://deckbox.org/sets/529877
As you can see I have far more ramp than you do and I still felt I needed 24 lands. There would be several times I'd get stuck on 1 land and playing against supreme verdict or other removal means your mana dorks might not be enough to get there. Courser domri and the other cards like garruk help make sure you stay on live draws when you need them though. You probably don't have access to all these cards so i'll make some more simple suggestions.
Swordwise Centaur is strictly worse than kalonian tusker no reason not to have a set of these in the deck.
EXperiment 1 is an awesome card in this deck, can't fathom why it's not in your list. Remove the scorpion for it asap.
ARbor colossus is also great, put that guy in there. get rid of the seering bloods. All 4 ghor clans should go in as well... Maybe over mortals resolve. Resolve is really kind of a sideboard card against heavy removal decks.
if you have xenagod out and attack with something then ghor clan it you can do some serous damage.