What you'll need:
- 2 Set Bonus from PvP set. This give you 25% dmg for your next special attack, which is really any spell that uses runes or runic power.
- Glyph of Resilient Grip. It resets your CD of your Death Grip whenever you death grip someone immune.
- Glyph of Tranquil Grip. This does so your death grip doesn't taunt the target.
Combining these three things, you will be able to spam your death grip on bosses, since they are immune to death grip, and you'll get the 25% dmg buff. I've used this in Molten Core recently and it works wonders.