I have to say, there have been so many "accidental" reveals that you start to wonder if they were accidental at all.
My distaste for these megas aside, they do present viable niches as "defensive mega evolutions" that previously were only truly filled by Mega Venusaur and Mega Blastoise (ZardX was clearly meant to be a bulky attacker, but WoW + Recover is useful on almost everything that learns it). Even then, Mega Stoise is more of a specially offensive tank what with its ability and stat gains.
Mega Sableye offers a brand-new defensive option with a single weakness, as well as boosted defense. Altaria, while certainly capable of offense, has a beastly defensive typing AND access to instant recovery. While Aerialate Mence will no doubt be threatening, lets not forget it has access to Roost, a great speed tier for a defensive mon, and a wide movepool (and of course, the rare Wish).
Mega 'Bro adds to our repertoire of defensive Megas and has a great typing for doing so. Sure, it loses Regenerator, but that isn't as big of a deal because it has arguably the most bulk of any Mega revealed thus far AND has instant recovery WITHOUT a SR weakness (sorry CharX and Mence) at any point. The boost to its already decent special attack lets it tailor its moves, as well; idk that it needs more than Scald (gg physical attackers), Ice / Fire / Psychic coverage to check what it needs to. Alternatively, it presents a fearsome option for setting and using Trick Room, thanks to increased bulk, power, and recovery. I wouldn't count it out as "useless" just yet.
I'm not sure what place Audino will hold, given that its low offenses make it a sitting duck, but it is certainly bulkier than Wigglytuff with Ghost / Dark / Bug / Dragon immunities and resistances. Audino will likely also hold the title of being the most physically defensive fairy (bye Granbull) and may compete with Sylveon in providing Wish / Cleric support. It'll be interesting to see where it ends up.
