Why use Heat Wave? Flamethrower over powers it entirely, with PP and everything. Uh, Earth Power gives more coverage on other threats. See it is hard to have his moveset to cover threats, why? Since HP [Grass] vs. [Ground] is always an issue, that is fixed by Earth Power, allowing him to follow up with [Grass]. Grass is meant for Swampert and Rhyperior, which is the most popular switch-ins for Arcanine. HP [Grass] OHKOs Swampert, and Rhyperior is overkill. Earth Power finally kills off Heatran which totally stalls Arcanine to bits with HP [Grass] without Ground. Then, you are left with being walled by bulky Waters. This is what makes Arcanine sucks, is because he lacks a real Grass or Ground special move except HP, because he needs them both at the same time, and you cannot have two different sets of IVs, plus you cannot have two of the same moves. Extreme Speed is helpful, but lowers the value in his moveset's coverage. Thunder Fang is getting now where if you have NO Atk EVs, it might take 4HKOs just to take down a Starmie. Which is useless being there. Overall, Heatran became one of the best special sweepers in the metagame because of Earth Power and Fire Blast combo paired with Dragon Pulse and HP [Grass], though Arcanine isn't blasted by SR weakness, and he doesn't have the greatest resistances. But, if he obtains Earth Power, then he will be moved to OU for sure.