Like the great Shofu mentioned in one of his live streams, talonflame is also hard walled by heatran and rotom-w ;)
Heatran maybe.
But Rotom-W can be 2hko if it's not as full health.
Rotom-W "bulkiest" set in the calc : +2 252+ Atk (custom) Brave Bird vs. 248 HP / 0 Def Rotom-W: 145-171 (47.85 - 56.43%) -- 35.55% chance to 2HKO
That's item-less Talonflame, if you give him a Sky Plate it goes :
+2 252+ Atk Sky Plate (custom) Brave Bird vs. 232 HP / 0 Def Rotom-W: 174-205 (58.19 - 68.56%) -- guaranteed 2HKO (Leftovers can't stop it either)
And a life orb :
+2 252+ Atk Life Orb (custom) Brave Bird vs. 232 HP / 0 Def Rotom-W: 188-222 (62.87 - 74.24%) -- guaranteed 2HKO
Obviously you want to try and switch your Rotom-W into an unboosted Talonflame, but if you can't you're in trouble.
Heatran can take hits better sure, but most of the time it doesn't carry anything that Talonflame can't outheal. Earth Power can't hit it, fire attacks are well, NFE, hidden power is at best Neutral, as is Dragon Pulse. Best it can do is roar it away or use Toxic.
+2 252+ Atk (custom) Brave Bird vs. 248 HP / 8 Def Heatran: 145-171 (37.66 - 44.41%) -- guaranteed 3HKO
Can still dish a lot of damage before being roared away too.
Obviously those calcs are flawed, because new sets will probably arise for those Pokemons in 6th gens, maybe more physically defense oriented. But with what we have here, Heatran and Rotom while better than most at stopping Talonflame, they aren't immune to failure.