RNG will probably mess that up pretty good. Even with that you'll probably end up occasionally getting 4-5 scorches in a row, etc. If you want a specific rotation you're probably better off doing a castsequence.

But, what I'd do, is a castsequence and a castrandom, and then spend 5 minutes in front of a practice dummy doing 2-3 minutes with each one and see which one does more DPS