Raw stats aren't everything ... Gabite has a base stat total of 410, and Monferno = 405.Things like Monferno and Gabite simply don't have the raw stats needed to compete.
Both higher than Ariados who has BST of 390.
Yet in the past I've used said spider to take out half a OU team with a little luck, some prediction and super effective attacks: Gengar (BST 500), Azelf (BST 580) and Swampert (BST 535)
Admittedly given Ariados lower base stats it would be difficult to accomplish this on a regular basis, but still this little example hopefully demonstrates that base stats aren't always the be all and end all.
Just something to think about ...