You're still citing it as a flaw of -atespeed that it requires a specific pair of Pokemon be on the field to get the benefit and ignoring that this is also true of Prankster Spore. In fact, -atespeed is less finicky about that, as switching in an -ate provider on the same turn an Extreme Speeder uses Extreme Speed still provides the full benefit, where Prankster Spore requires both Pokemon are on the field at the same time at the very start of the turn to be usable. Yet you're only citing this as a limitation of -atespeed and entirely ignoring that it's more true of Prankster Spore.
Your choices of "bopped by" are bizarre and nonsensical -Tyranitar is outsped and dies to one Close Combat, Heatran is outsped and dies to Earthquake, Aegislash is outsped and can be KOed by double Earthquake (Against Physically Defensive Aegislash Earthquake does more than 60% in Doubles off of both of Dragonite and Mega Pinsir), and Mega Diancie needs to spend a turn Mega Evolving during which time Dragonite and Mega Pinsir can potentially be getting off a Dragon Dance -and if instead it goes for the first-turn attack it's risking being KOed by, again, Earthquake, not even getting into the fact that Dragonite gets Iron Head. 8MSS doesn't even apply here -one decent moveset will kill all of those at the same time while still having room for Extreme Speed. I'm leaving out the part where Multiscale is a big deal, too.
208 Atk Mega Diancie Diamond Storm vs. 0 HP / 0 Def Multiscale Mega Pinsir: 236-282 (87 - 104%) -- 25% chance to OHKO
Grabbed straight from the calc for Doubles Mixed Attacker Mega Diancie. Yeah, Mega Pinsir has good odds of surviving Diamond Storm. That's a doubly super effective functionally 75 BP move off a STAB attacker with 160 Attack and a good chunk of investment. Actually OHKOing Mega Pinsir backed by Dragonite is difficult without high power STAB Stone Edge (Terrakion will get the KO every time with Stone Edge, no need for a Life Orb, but anything weaker is at risk of not getting it), and Terracott is defeated by the simple expedient of Extreme Speeding Whimsicott out of existence -or Terrakion, as it takes more than 65% from Mega Pinsir's Extreme Speed and only slightly less from Dragonite's. (It's not like Whimsicott can do much of anything to Mega Pinsir and Dragonite, aside from breaking Multiscale) Hell, Mega Pinsir's Feint+Dragonite's Extreme Speed is a KO on Terrakion, so it can't even necessarily stall with Protect!
It's also baffling to me that you're ignoring that Prankster Spore outright loses to Aerilate Extreme Speed -even your own argument provides a clear utility to Aerilate Extreme Speed, even if you hold to the belief that Aerilate Extreme Speed is otherwise dubious.
I also find it baffling that you're playing up the utility of shutting down an enemy Pokemon and ignoring the superior utility of simply vaporizing them. Yeah, Spore is nice (You know, ignoring Lum Berry and Safety Goggles and so on) but KOing the enemy is nicer.
The only real flaw with the Dragonite+Mega Pinsir core is that it's incompatible with other Megas... and honestly, the only Megas that really leap out as the sort of thing you'd really hate to be missing out on are banned anyway. (Medichamite, Kangashkanite, Mawilite) Unless you're going to argue that Mega Sableye is going to be amazing, but you seem to be dismissing it out of hand, which seems silly to me given that it's a hard stop to Prankster Spore that comes with innate recovery and would love to benefit from any number of partners. (Such as another Prankster)
Your choices of "bopped by" are bizarre and nonsensical -Tyranitar is outsped and dies to one Close Combat, Heatran is outsped and dies to Earthquake, Aegislash is outsped and can be KOed by double Earthquake (Against Physically Defensive Aegislash Earthquake does more than 60% in Doubles off of both of Dragonite and Mega Pinsir), and Mega Diancie needs to spend a turn Mega Evolving during which time Dragonite and Mega Pinsir can potentially be getting off a Dragon Dance -and if instead it goes for the first-turn attack it's risking being KOed by, again, Earthquake, not even getting into the fact that Dragonite gets Iron Head. 8MSS doesn't even apply here -one decent moveset will kill all of those at the same time while still having room for Extreme Speed. I'm leaving out the part where Multiscale is a big deal, too.
208 Atk Mega Diancie Diamond Storm vs. 0 HP / 0 Def Multiscale Mega Pinsir: 236-282 (87 - 104%) -- 25% chance to OHKO
Grabbed straight from the calc for Doubles Mixed Attacker Mega Diancie. Yeah, Mega Pinsir has good odds of surviving Diamond Storm. That's a doubly super effective functionally 75 BP move off a STAB attacker with 160 Attack and a good chunk of investment. Actually OHKOing Mega Pinsir backed by Dragonite is difficult without high power STAB Stone Edge (Terrakion will get the KO every time with Stone Edge, no need for a Life Orb, but anything weaker is at risk of not getting it), and Terracott is defeated by the simple expedient of Extreme Speeding Whimsicott out of existence -or Terrakion, as it takes more than 65% from Mega Pinsir's Extreme Speed and only slightly less from Dragonite's. (It's not like Whimsicott can do much of anything to Mega Pinsir and Dragonite, aside from breaking Multiscale) Hell, Mega Pinsir's Feint+Dragonite's Extreme Speed is a KO on Terrakion, so it can't even necessarily stall with Protect!
It's also baffling to me that you're ignoring that Prankster Spore outright loses to Aerilate Extreme Speed -even your own argument provides a clear utility to Aerilate Extreme Speed, even if you hold to the belief that Aerilate Extreme Speed is otherwise dubious.
I also find it baffling that you're playing up the utility of shutting down an enemy Pokemon and ignoring the superior utility of simply vaporizing them. Yeah, Spore is nice (You know, ignoring Lum Berry and Safety Goggles and so on) but KOing the enemy is nicer.
The only real flaw with the Dragonite+Mega Pinsir core is that it's incompatible with other Megas... and honestly, the only Megas that really leap out as the sort of thing you'd really hate to be missing out on are banned anyway. (Medichamite, Kangashkanite, Mawilite) Unless you're going to argue that Mega Sableye is going to be amazing, but you seem to be dismissing it out of hand, which seems silly to me given that it's a hard stop to Prankster Spore that comes with innate recovery and would love to benefit from any number of partners. (Such as another Prankster)