Mega Slowbro with Shell Armor and Mega Audino with Normal/Fairy and Healer are apparently leaked. I don't like the fact that my Megabro has no Regenerator.
But for real though, it's not as bad as it seems. Mega Slowbro is an unkillable Crocune. Mega Audino is immune to Ghost and Dragon, resists Dark and will heal any status effects in VGC.