As far as your rotation goes i see a couple flaws. I see the rotation as this.
1. Crushing Darkness(Once CD is over reapply)
2. Affliction(Keep applied at all times)
3. Thundering Blast(It critically hits all targets affected with affliction.)
4. Chain Lightning( It stacks up to three times adding a bonus of 3% total dmg. So keeping it at 3 stacks would be good IMO but getting there will require some time due to CD)
5. Lightning Strike(Obviously 3 stacks necessary)
6. Force Lightning( On proc)