Absolutely. With huge power and two good types at its disposal, diggersby can hit very hard. Harder then Azumarill, who it has higher speed than as well, as well as access to quick attack to nail faster Pokemon. It also has a great range to boosting moves to become even more deadly, with agility, swords dance and even bulk up to play with. A huge power boosted return or earthquake can ruin a lot of stuff, and even quick attack's measly 40 base power is formidable when coming off of huge power with a type attack bonus and swords dance. It's ground typing makes it immune to thunder wave, too, making it very hard to slow and paralyse. It's a fantastic offenisve mon.
But only with huge power.
While it does get get some interesting moves to abuse like super fang, but while huge power isn't the only string to Diggersby's bow, it doesn't have much else to work with. It's defensive typing leaves it with 4 very common weaknesses and a lot of things it can be hit neutrally by. Plus, while not weak in defence, it isn't really amazing either, meaning it can't really abuse its Cheek Pouch ability to it's fullest. And while pickup is a great ability for a filler mon in game, it's a waste of a perfectly good teamslot, and Diggersby has far too many stellar offensive options to waste on that.
As someone that has used huge power Diggersby in OU competitive, I can fully say that huge power definitely makes it worth using. It's resistance to electric (especially thunder wave) good offensive typing and great boosting moves and reasonable bulk make it able to grab momentum easily and make good use of it. And from experience, anything that performs well in OU competitive simply annihilates in game. Huge power Diggersby is great and more than makes up for its low stats (actually pretty fun to use, too), and while it's other abilities are not bad, they're just nowhere near as good and waste it's potential.
Word of warning, though. Like Medicham and Azumarill, if it looses it's ability from a move like gastro acid, it's all but screwed unless you swap it out. Aside form that, it's excellent. It would make one hell of a bruiser on an in game team. Plus, it's a good laugh to use.