DPS display could easily be solved with a system already in game.

[Zaft]

snip

You need to look at AoE as potency per target. Fire 2 has a potency of 100 while Fire 1 is 170 and Fire 3 is 240. Firestarter is a 40% proc rate. Additionally, Fire 2 takes 0.5s longer to cast than Fire 1. Now, you can easily crunch these numbers to see how many enemies need to be in AoE range before Fire 2 overtakes Fire 1 with Firestarter procs as a DPS gain.

(the answer is 3)