Auride, you'd have to use 108 EVs in SDef if you want to guarantee the survival of Overheat. You could use 84 though which makes it so Charizard can only get a OHKO 6.3% of the time. Using the 84 you still can have enough EVs in Def to survive adamant 252 Iron Head from Aegislash.
I replied on your profile because I didn't have time to do a full rate and just adding a damage calculation wouldn't be considered giving a rate.
Also, it'd be worth testing Tyranitar on your team over Barbaracle. I used to use a defensive spread, but it still did enough damage to be worthwhile. The sandstorm it brings up is nice for getting rid of any Focus Sash Pokemon you may run across, which could include support Talonflame.