Where did you do your calcs, as the showdown damage calc is giving me thisNot QC but I'm seeing 64 Def EVs being thrown in to ensure survival against CB Talon's Brave Bird after rocks, but the problem is that those EVs don't actually ensure survival, so the wording in the analysis is false.
252+ Atk Choice Band Talonflame Brave Bird vs. 0 HP / 64 Def Haxorus: 238-282 (81.2 - 96.2%) -- 56.3% chance to OHKO after Stealth Rock
In order to ensure survival, you need 156 Def EVs, and there's no reason to invest so heavily into Def.
Actually now that I think about it, 64 Def doesn't do much for you other than hoping for a low damage roll, so you might as well go with an Adamant 252 Atk/36 Def/220 Spe spread instead since that allows you to still always survive CB Talonflame at full health without rocks while giving you maximum attack power and enough speed to outspeed Jolly Mamoswine. I believe that spread could apply to both the DD and SD sets, though for the DD set an alternate Adamant 120 HP/252 Atk/136 Spe spread allows you to outspeed +1 Adamant Dragonite and Gyarados after a boost while granting more all-around bulk:
252+ Atk Choice Band Talonflame Brave Bird vs. 120 HP / 0 Def Haxorus: 256-303 (79.2 - 93.8%) -- 43.8% chance to OHKO after Stealth Rock
Just my two cents.
Just noticed that the calculator is set to jolly for talonflame by default *facepalm* Looks like its not worth adding bulk in that respect, are we back closer to something like 252/252 again?