Right.
The Chant can buy you the 3rd turn, while you play something for 2 mana. In that use, it's good.
Post-Geddon, though, it's not terribly useful, since the only thing it will be good for, for awhile, is preventing attcks from the opponent's creatures. But, hopefully they don't have any. Besides, that particular use of Chant costs WW, which might be hard for you to cough up after an Armageddon.
As for the rest of the deck, going 3-color is very risky in a 'Geddon strategy.
I can see where a Lair might be useful -- by tapping 3 lands, laying a Lair and bouncing one of the tapped lands, then playing 'Geddon. You can save one of your lands this way and get a jump on your opponent.
My instinct, however, is to shy away from this, as it really requires you to play 4 Lairs, which I really don't like to do. Aside from that, there's the problem of not getting the colors you need.
Add to this the fact that Shivan Wurm costs 5 mana to play, which is exactly one more than you want any creature to cost in a 'Geddon deck. It's the same reason why Mungha-Geddon never made it.
So if you really want to go 3-color (to take advantage of the Lair's gating effect) I recommend you go with Sparkcaster, a 5/3 gater for 2RG that pings when it comes into play. It's plenty big enough to hurt your opponent and can be played in the tempo that 'Geddon decks need to be played.
I'd also remove the Orim's Chants (sorry) in favor of another Tangle Wire and 2 Disenchants. You might even want to use Aura Mutation, if you don't expect artifacts to be a problem.
Finally, I'd pull the Armadillo Cloaks in favor of Blastoderm (the 4th Chant make rom for the 4th 'Derm) because, well, why aren't you playing Blastoderm? You'll probably get it out on turn 3, and the Fleetfoot Panther resets it.
See, with more creatures, and good interaction between them, you can hold your own in games where you don't draw the 'Geddon.
One more note: beware Simoon. Fires (and any other R/G) will wipe out your creature-mana base, then beat the crap out of you. I'm not suggesting any changes for this, only caution when playing against R/G.