What I do as an OT in this fight is to keep using Heavy Swing when I know Garuda is about to spawn adds so when the adds come down, I can use Skull Sunder on the closer add. If it's red, great, combo in a Butcher's Block and pull it away from party. If it's green, stop hitting that add and let dps take aggro. Also, make sure you don't stand between main-tank and Garuda so you don't eat Slip streams. This part and the double tornado part is what make or break a Garuda run. Everything else is easy.