Your Shaman's DPS is surely lacking. For 1 Tank 2 Healers, you will need lots of raid DPS to be able to burst down Deathwing on P2 before Tetanus overwhelms your healers. I also don't think Warriors are the best tanks for this due to your limited cooldown arsenal.
However, there is something you could try. Instruct your raid to focus fire down one of the Terrors and after one of them dies have one of your raiders (say, the Paladin or the DK) taunt and kite the Terror until your Tetanus stacks drops. Afterwards pick it up again and finish killing it. Proceed to killing Deathwing. You could also gear for more Stamina in this particular fight.
Having tried a variety of compositions for this fight (1 Tank 2 Healers, 1 Tank 3 Healers and 2 Tanks 3 Healers), I would recommend going 2 Tanks and 3 Healers, if you have the luxury of doing so. Of course, anything from 1-2 Tanks and 2-3 Healers works, but that comp. ensures maximum control; phase 2 is cake with that comp.
Depending on your healing comp you could do with 2 Tanks 2 Healers (ie, a Resto Shaman and a Disc Priest have very good mitigation cooldowns for the Elementium Bolt; and since you have 4 piece T13...) but I'd go the safe way. After the Mutated Corruption dies, one your healers can go DPS mode anyway. This worked greatly for us as our Resto Shaman could heal like there was no tomorrow and would recover all of his mana through the Telluric Currents talent by going DPS afterwards.
You might have to blow a BL on the last platform depending on your raid DPS, to ensure Deathwing does not cast Cataclysm, but that's alright. If you can save it for P2 that's great, but not really necessary. Once again, P2 is cake with this comp.
As an extra note, Feral Tanks seem to be great on this fight. On my raid he could dish out 31K DPS.