45% crit ? I have 60% crit.Precast Fireball/pyro depending on your potion (prolonged = pyro, deadly grace = fireball).
Use Mirror Image
Cast Cinderstorm and use combustion right before the cast ends (Use meteor instead if you are using that for whatever reason).
Cast Phoenix Flames (And Fire Blast if your initial precast didnt crit)
Cycle Pyroblast -> Fire Blast -> Pyroblast -> Fire Blast -> Phoenix Flames -> Pyroblast etc till everything is used (If you have dragons breath helm make sure to use it at the end of the combustion)
After your burst is over you use (in order of priority)
1) Dragons Breath with Helm
2) Cinderstorm/Meteor (If meteor, you should use it only once between combustions. The explanation to this is at the bottom).
3) Phoenix Flame if you have 3 stacks ONLY
4) Fireball/FireBlast/Pyro combos
you constantly cast fireball if the above top 3 priorities are unavailable. If during your fireball casts you get a heating up, you cast Fire Blast and instantly use pyroblast to chain at the end of the fireball cast. You NEVER use pyroblast without a fireball at the same time (if you want an explanation of why, message me and ill explain things in more detail.)
Repeat the above till your MI/Combustion is back and from there you repeat the opener.
Math for Meteor:
If meteor is a 45s CD and Combustion is a 120s CD. Your meteor will come up at 45s, 90s, 135s. That means if you do NOT use it on CD and only use 1 between combustions, you will sit on a meteor for (120-90)s which is 30s. If you sit on a meteor for 30s, thats essentially 66% of a meteor 'wasted'. Combustion guarantees a crit (i dont think meteor applies ignite so that mastery buff would be irrelevant). If combustion guarantees a crit, that means it doubles the damage of meteor or essentially an extra 100% of a meteor. If you are wasting 66% of a meteor by saving it, but getting 100% extra damage. However, mages already have circa 45% crit chance currently, so the odds of meteor not critting would be 55%. So essentially we can add (0.45*66) to the 66% 'wasted' meteor. 0.45*66 is 95.7% 'wasted' meteor. Only using 1 meteor between each combustion means we waste 95.7% of a meteor but we gain 100% of a meteor. Ofcourse, 100 > 95.7. Therefore I worked out that its better to save meteor than not. If you cannot fit another combustion in before the fight ends, you should use meteor on CD then ofcourse. If anyone disagrees with my math please let me know. (Sorry for the crappy lay out, wanted a more explanatory approach to the math rather than complete numbers).
I did all these sims and theorycrafting myself so it might not be perfect but im pretty confident in my results tbh