Pathfinder 2e and D&D 5e are similar games, but key differences (action economy, saving throws, the skill system, and bounded accuracy in general) separate them enough that mental effort is required to translate
Combustion can be argued to be better than Lightning Bolt, same range, swap the line effect for persistent damage that will do overall more damages than Lightning Bolt. At higher level you don't have as much an issue, but its' more due to the scarcity of higher levels Focus spells. Th...