Seconding this, Mawile is really meh tbh, at least not A+ material. I've faced it many times and every time I literally just bring Pdon and it isn't a problem to deal with. It does beat a couple of things, but its matchup against primals is just so bad (Primal Kyogre with positive SpA almost always OHKO's it with Origin Pulse), especially pdon, which is on more than every other team (might be overexaggerating here but you know what I mean). B might be a bit harsh due to its matchup against like something else than primals, maybe B+.
Latios C+ -->B
What, C+? This thing is far from perfect, but way closer to perfect than Cherrim and Mega Houndoom. It is a Tailwind setter, and a Dragon that threatens both M-Mence and M-Ray pre-m-evo, and forces them to Protect, on which turn it can set up Tailwind and really be a threat. It has some really nice coverage options as well such as Grass Knot, and it does a ton to any Pdon, as well as resisting both its stabs. It also has a decent matchup against Primal Kyogre, although Ice Beam does a ton to it. In short, it is nothing amazing, but a neat Pokemon that defiently is on par with Mienshao and Goodra imo (if not better).