Don't generate aggro with Gokk'lok's Shell

I was tanking an add on Dark Animus HC yesterday, and on one of the trys I used my Gokk'lok's Shell (the description on how to get it is in the 2nd wowhead comment) before pulling. I started DPSing my add (while still being in the shell) but he ran to an healer and I had to take off the shell to take back the aggro.

I only tested it once since it could lead to a wipe, but I'm sure it's due to the shell, since he came back instantly when I took it off. Actually I'm not sure if you don't generate aggro, but you definitely don't get the aggro of the mobs.

So basically :

1. Use Gokk'lok's Shell.
2. Stay in it.
3. While you're in the shell, you won't take aggro.