"I want fire to be better than arcane, because that's the playstyle I want"
If you try to force and play a sub standard spec, you'll never be happy. How are you any different from any other class going through the same exact thing in every single point in WoW's history.
And for those that didn't know yet, combustion is off the gcd. It's actualy very nice to use when you got a trinket up. For those running a DFO foe exmaple, hitting combustion when that is up giving you 3-4 crits, depending if you get a ghost charge pryo into it, with +700-1200 spellpower with a 70-100% crit chance that deal +50% crit damage.