Pros of Diggersby: He doesn't take up a Mega Slot, so you can have a powerful wallbreaker and still have a Mega Evolution on your team. To set himself from the Mega wallbreakers, he can hold other items, so he can use a Focus Sash to make up for his middling bulk, or a Choice Scarf so he isn't overly dependant on Quick Attack to finish off a foe, thus creating some flexibility with his sets and unpredictability when he's approaching someone. Normal / Ground coverage is only resisted by Skarmory, which has gone down in popularity, Aerodactyl, which has gained some popularity but doesn't take kindly to Wild Charge, and Trevenant and Gourgeist, which are never seen these days, so he has freedom with his remaining two moveslots.
Cons of Diggersby: His Attack is literally the only good stat he has when factoring in Huge Power, as his average bulk and mediocre Speed greatly limit his revenge killing role. Mega Heracross can tank hits well to make up for his low Speed, while Mega Medicham makes up for lack of bulk with good Speed; Diggersby has both their flaws but the only real strength that he has to cover said weakness is being able to hold an item. You also only have a distinct vulnerability to priority, with weaknesses to Aqua Jet, Ice Shard, and Mach Punch, and Talonflame's Brave Bird being able to OHKO almost every time with Stealth Rocks.
Right now, I'm against Diggersby moving up, as his bad stats outside of Attack with Huge Power, bad defensive typing, and over-reliance on Quick Attack or Choice Scarf to outspeed most relevant threats means that he requires a good amount of team support to perform well. Keep Diggersby at A-.
-> C-
