It seems better to use your second move in the enmity combo due to the animation speed. If you have a precharged BB/RoH it takes a couple seconds for it to register due to the animation.

For Turn 1, usually we mark Caduceus before pulling. When they split all you should have to do is hit tab and you'll be on the 2nd one. Have your Skull Sunder preloaded and just hit it, then run away with the snake using Tomahawk.

For Spiny, as OT I provoke it off to the side and use a couple Tomahawks/Shield Lobs to ensure it stays on me. Everyone else stacks behind Garuda to keep the other plumes on them so they can AOE them. For the Sisters phase I let Spiny go to whoever it feels like, then voke it at 2, or if it's on me, I'll move in as close to the tank as I can inside of my little vortex area and he taunts it off me at 2.