You're kidding, right? Right now, Sharpedo has 120 attack and 95 speed. Assuming, and this is the only assumption that I'm going to make, that Sharpedo gets the rough equivalent to a life orb boost in attack, it will have around 155 to 160 as a base stat. Strong Jaw plus STAB makes Crunch a base 180 physical attack with no drawback. Compared to M Gardevoir, who has a 165 base special attack, and a 175.5 base power move with no draw backs. With Protect, it has a very usable speed, greater than Talonflame's, and an offensive move that's roughly equivalent (maybe a bit less) to M Gardevoir's Hyper Voice, and a STAB priority.
Even without such a high attack boost, and with piss poor bulk, Mega Sharpedo should be in no way inferior to Base Sharpedo.