User blog comment:Kogath/Monster Hunter XX Discussion/@comment-27120688-20170318201839/@comment-6050823-20170318224951

What he basically means is the Deviant cap is no longer Level 1 - Level 10. It now is is Level 1 - Level 15 for the 12 original Deviants: Redhelm Arzuros, Snowbaron Lagombi, Stonefist Hermitaur, Dreadking Rathalos, Dreadqueen Rathian, Grimclaw Tigrex, Silverwind Nargacuga, Drilltusk Tetsucabra, Crystalbeard Uragaan, Thunderlord Zinogre, Hellblade Glavenus, and Deadeye Yian Garuga.

The 6 new Deviants are G-rank exclusive and only have 5 Levels: Massacre Demon Diablos, Blue Thunder Lord Astalos, Silver Ridge Gammoth, Heavenly Eye Mizutsune, Hidden Haze Malfestio, and Armor Shredder Shogun Ceanataur.

Still not 100% about the Super Deviants, but I do know they're in-game. From what I what heard, these individuals are much faster and more unpredictable than any normal Level 15 Deviant.