I'm not fully jumping into the discussion right now, but I wanted to say a couple things.
252+ Atk Silk Scarf Huge Power Diggersby Extreme Speed vs. 4 HP / 0 Def Keldeo: 222-262 (68.5 - 80.8%) -- guaranteed 2HKO
Keldeo can only revenge, and it has to be healthy.
Also, MScizor doesn't outspeed, and it loses to Fire Punch and even 252 HP takes over half its health from Precipice Blades. 4 HP can take 80% from Precipice, meaning even against Diggers lacking Fire Punch it's a shaky check, and no matter what it comes out severely weakened.
As I said I'll post more later, but I'm very solidly pro-ban.
252+ Atk Silk Scarf Huge Power Diggersby Fake Out vs. 4 HP / 0 Def Keldeo: 111-132 (34.2 - 40.7%) -- guaranteed 3HKOoffensive checks are aplenty, just like with mega medicham. Aerodactyl, Mega Scizor, various fast mons can outspeed and take a espeed. Even stuff like keldeo can take SS Espeed barring a crit (70%).
252+ Atk Silk Scarf Huge Power Diggersby Extreme Speed vs. 4 HP / 0 Def Keldeo: 222-262 (68.5 - 80.8%) -- guaranteed 2HKO
Keldeo can only revenge, and it has to be healthy.
Also, MScizor doesn't outspeed, and it loses to Fire Punch and even 252 HP takes over half its health from Precipice Blades. 4 HP can take 80% from Precipice, meaning even against Diggers lacking Fire Punch it's a shaky check, and no matter what it comes out severely weakened.
There are other FakeSpeeders. I've been using Braviary over Diggersby since the beginning of gen VI and never had any problems with the sweepers that Diggers keeps in check. Braviary is the best of them, but there are several mons that can viably run the set. Have we all forgotten about Ursaring? Sure, it takes residual damage every turn, but it's even stronger than Diggersby is and has the elemental punches and Play Rough, although it lacks Knock Off.The issue with banning diggersby is all the broken shit that comes in. It excessively centralizes sableye to handle those sweepers, and could lead to the banning of moves...or even types...*cringes*. Where normally we can just say the game will adapt or we can ban the broken shit, the problem becomes that this would require a fundamental change to the tier, one that may not be for the best.
As I said I'll post more later, but I'm very solidly pro-ban.