In the Dragonflight features trailer, Blizzard revealed that you must pre-purchase Dragonflight in order to access Evokers on November 15th.
Dracthyr can only be one Class, Evoker. Dracthyr are the only race that can be Evokers making this the first completely unique and discreet Class/Race combo. The Evoker is a Mail wearing, Intelligence based, mid-range class with two specializations, DPS and heals.