With Max EVs and IVs, Huge Power 85 base attack is the euivelant of 219 regular base attack. This is not being eclipsed by a whole lot. Certainly nothing the itemless Megas Have to offer.So far, every Mega has gained a full 100 points to its Base Stat Total.
That bodes ill for the potential utility of Mega Mawile, who would end up with a still-poor 480 if the patterns hold, and whose Huge Power boosted base 85 Attack is being eclipsed by Megas of other, more well-rounded Pokemon.
If Game Freak was trying to use Megas to stimulate balance, they've not done a very good job of it.