Mylune as a mission champion and Brightwing are quite useless. Mylune's bonus is essentially nothing and Brightwing's IS nothing. You don't rely on it for AoW/DGWs (why would you?) and the gain you get from it when it does proc is minimal. If anything, it's best paired with one of Moroes's Dinner Guests, but you get those enough and use them so sparingly that it shouldn't really matter.
Except there's still older missions and overall Feral is slightly more common and Resto is slightly less common. Also, see my next point below.
Except both Meatball and Moroes can easily 100% any mission by themselves, and as I pointed out a page ago, excluding needing required counters (Cursed basically), Moroes can 155% ANY 0% base success mission with just himself and a Keeper if Minions are on it. That's batshit insane to not counter a single thing and still get 155% AND have an extra slot leftover! Of course Meatball could do 180% with a Keeper if you build him for T2 troops, but I like him having high Reduction.
Overall, the specialization split isn't nearly as vital as having all the ability counters covered, which is why you want to balance those heavily and use DGWs to fill the gaps.