Cast combustion which can be casted while casting other spell and isnt on the GCD:
Get free instantly Rune of Power for +40% dmg while also getting +100% crit from combust
Infernal Cascade conduit: Get 12.6% fire damage increase for each fireblast up to 2stacks. So 25.2% fire damage.
Can play the crit = damage increase legendary for even more burst damage
Or triune to protect Combust, doesn’t matter you cast meteor double fireblast pyro and your target is dead from a single gcd.
So you get a total of 65.2% damage increase (without the damage legendary) and 100% crit chance on 1.75 crit modifier.
Add Dark Archangel for more fun.
Cooldowns stacking congrats you need nerfs aswell.