On boss fights be sure you are using curse of elements. You might pick up Soul Siphon. I would say stop using Shadow Bolt, as I never use it except on Nightfall procs, but it's hard to convince people of that. Shadow bolt is shadow damage, but it is a destruction talent. You will get the most output by keeping your DoT's all up 100%. Especially with your talent spec. The more DoT's you have up the higher your dps is because your DoT's fuel procs of other talents.