Don't put Conflag in your macro because your macro will block if Immolate isn't up. This can happen if your macro starts with /assist <tank> and your tank switches targets between immolate and conflag. The big problem is that once this happens, you're pretty much stuck and have to go to multi-button dps.

A bit of advice:

1. Spend some time on the heroic target dummy with recount to see what's up with your dps. You'll want to adjust things over time.
2. Consider your party synergy. Keep in mind that surv hunter and dest warlock both can have replenish.
3. If you're struggling with regular instances, do something easier and work your way up. Mainly it's practice.
4. Single box your toons with other parties and raids both to gear up and to learn the class.