I 100% agree with this. Altaria is an extremely versatile and effective in all of it's roles. With Greninja gone one of Altaria's biggest checks is now gone. One of the only mons that can deal with her dd set now are scizor, unaware clefable and ferrothorn, and that's only if it isn't carrying fore blast for two of them. It's fantastic defensive typing, good stats and amazing movepool allow it to be completely unpredictable and make it a huge threat.
Scizor lost to mixed Altaria with Fire blast on the switch in and if the Scizor is not banded , Alt can live one BP
4 SpA Mega Altaria Fire Blast vs. 248 HP / 0 SpD Scizor: 416-492 (121.2 - 143.4%) -- guaranteed OHKO
Unaware Clefable is really , really passive against max att adamant Altaria if SR are still ups on the switch in
252+ Atk Pixilate Mega Altaria Return vs. 252 HP / 252+ Def Clefable: 186-220 (47.2 - 55.8%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
Ferrothorn obviously , lost to mixed Fire blast or even Special set , so i think it just show up Altaria's versatility.
4 SpA Mega Altaria Fire Blast vs. 252 HP / 168 SpD Ferrothorn: 264-312 (75 - 88.6%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery ( so, can't switch in.)
252+ SpA Mega Altaria Fire Blast vs. 252 HP / 168 SpD Ferrothorn: 360-424 (102.2 - 120.4%) -- guaranteed OHKO
Same for Skarm :
4 SpA Mega Altaria Fire Blast vs. 252 HP / 4 SpD Skarmory: 230-272 (68.8 - 81.4%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
252+ SpA Mega Altaria Fire Blast vs. 252 HP / 4 SpD Skarmory: 312-368 (93.4 - 110.1%) -- guaranteed OHKO after Stealth Rock
And Alt is obviously one of the biggest counter to M-Sableye a HUGE threat , the only 'mon who can counter ALL Alt sets is M-Venu in OU , who is really low in usage since ORAS.
So , i agree with
Altaria and probably Clefable in S rank.