Actually, Rapidash has 105 Base Speed. The -2 Speed would only make it lose to Lopunny and Magnetric, none of which is a threat to BP Rapidash's main purpose. Get in on a Fire Attack, Sub, then Agility. Flare Blitz is for coverage, and speed does not really matter after an Agility.
In fact, I have been using a really bad one before this one, it has 23 IVs and Jolly, and it has not given me any problems.