People just overcomplicate their rotation by thinking theres some complex adaptable priority system that changes often.
Here are some things that become super simple if you assume Kindling and ok gear:
ROP, ~1.5 Seconds before Combust becomes ready and the second charge directly after.
Phoenix's Flames, cast one during Combustion and the remaining ones during the next ROP Phase.
Flame On, Only use it during Combustion.
Fireblast, Use two stacks until 26 seconds before combust, One stack until 13 seconds before combust.