combustion is a fire mages biggest dot, and the damage of each tick is calculated by the sum of all the other dots on the target. So, if I'm playing by hand I use addons to moniter the size of the dot on the target from ignite. Never ever do we push the combustion button unless ignite is ticking for more than 20k. Your cc just checks to see if there's a living bomb, pyroblast dot, and ignite dot on the target. Idk if it's possible for hb to see the size of the ignite tick or not, but, if so, if you could add some kind of if statement for it to not use cumbustion unless the ignite tick is >20000 or a user defined variable, all the fire mages that are using your cc would love you forever and ever.
Hope that made sense