Agree to an extent, though some pokemon like Venusaur were "usable" and OU, but were Mega-Evos well-spent due to filling an entirely different niche. I'll agree, something like Blaziken, which does the SAME EXACT THING as it's non-Mega'd form more or less, was a complete waste.
Eh, ignoring my avatar, I don't think Blaziken was a total waste of a Mega. The ability to hit hard without a single boost (and no LO recoil) is a lot more useful than you might think. It helps a lot in Doubles/Triples to be able to wreck things from the start. In the item clause world of Nintendo formats and Battle Maison, freeing up LO and Leftovers is rather handy. It may not be something like a Mega Absol in terms of filling a different niche, but total waste isn't at all what I'd call it. That's just me, though.
Well, here's one I just realized; Nintendo/Game Freak did not bother to ban any of the past-generation Legendaries from Random Matchups. This has resulted in Japanese players, who had PokeBank for a short time before it went down, being able to stack teams full of Ho-Oh, Lugia, Arceus, etc.
Really, A+ on the forethought.
Oh god, really? Another reason to avoid random matchup for awhile. Aside from the fact that not all of them are bound to be EV'ed, that's just annoying.