Nivmagus Elemental, I know you shot this down earlier on account of the chimaera, but I suggest you reconsider...My arguement: He fits your tribe theme. He gives devotion to red and Blue. He eats spells in a pinch and he's a 1 drop 1/2! Any spell you cast will trigger pyromancer prior to being consumed. You don't have to eat every spell, just one's that fizzle or get countered for whatever reason. That guarantee's value. Plus since you run so many instants, a cute little combat trick by casting spells to buff him for the block may leave your opponent with their mouth hanging wide open. Your fear of spells not going to the graveyard is completely in your control.The hardest decision is what to swap him in for, that and maybe consider Ember Swallower... as a sideboard idea. /shrug
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Mana fixing can make or break a deck. Command Tower, the dual lands from the Eventide/Shadowmoor block are pro, & Evolving Wilds/Terramorphic expanse could be considered. I know you don't want to run heavy in the artifact section, but expedition map is always worth looking into. When I run Green, I like Yavimaya Elder, something about 2 lands and a draw that just gets me :) I didn't see an angelic destiny... look into that as well. All in all, nice take on a Naya EDH.
Check and checkmate.
I recommend you work on your mana fixing, Armillary Sphere, Expedition map, Darksteel Ingot, perhaps spells like Cultivate & Kodama's Reach. If you like creatures, Yavimaya Elder is a wonderful card. Vivid grove/meadow/creek would be slightly better than say your cycle lands.... Replace Prahv for Kor Haven. If you're worried about your mana curve Temple of the False God could help. I wouldn't recommend spending money on them, but Karakas, Strip Mine and perhaps Gaea's Cradle are all pro in EDH. If you enjoy the 1 creature swing, Vorrac Battlehorns is awesome. Worldy Tutor and Enlightened Tutor might be worth considering. Since Rafiq is your commander, (and I only say this because I would love to make a deck with him as the commander as well) I recommend looking at your entire theme concept, keep your exalted stuff, but if you have "fluff" cards replace those with cards that can buff for cheap (Giant Growth or Might of Oaks comes to mind) and protect Rafiq/allow him to attack un-impeded (Swiftfoot boots, Trailblazer's boots, Rancor). Since EDH tends to have mutliple board wipes, Creeping Renaissance or Restock wouldn't hurt. Lastly, Garruk Wildspeaker is a wonderful Planeswalker, Venser, the Sojourner and Elspeth, Knight-Errant can both see to it that you succeed. At a minimum, run a board wipe or two (Wrath of God, Route, Day of Judgement), the reason being is that if something is on the field that you can't target, a global effect will still grab them up. Drop the life gain theme if you can, 21 commander damage from a single commander will kill you regardless of life total, so life gain isn't as important as Removal or situational survivabilty (Fog, Orim's chant, Silence). I hope this helps. Great premise.
I would consider using Sliver Legion as your Commander. While Sliver Overlord is an admirable choice, if it were to fall into your opponents hands (given enough mana) all your Slivers could be turned against you rather quickly. I've seen it happen. Sliver legion as a Commander would allow you to cast and swing for lethal in a single turn given playfield advantage. Play test both and see which one people consider more of a threat.