Forgot to post thoughts. Ah well: Luxray has a nice niche as a status-immune DDer but is not enough, I don't care about Thundurus although Electric/Dark is pretty cool, Arcanine is fucking broken (fancy that adding Normal actually improved something that's not a ghost) but might've been decent with either buff alone, so that leaves the interesting buffs for M-Latios, patron of overshadowed Megas.
Mega Latios + Dragon/Ghost and Analytic
Honorable Mention: Thick Fat Gogoat.