You do realize that two different teams work on the two different game modes.?
Additionally DF just had a full talent tree redesign this expansion. Which, I would say is significant. Several classes have had talent tree re-works as well. Which are way more changes than classic, and even season of discovery.
They are not changing classic. They are having a season of discovery. Which is a server with different aspects. The game will be level capped at 35 at the start. Then incrementally increased. They are not changing all the classes and specs in Classic HC or Classic WoTLK/Cata.
Did I miss something at Blizzcon? What new spec? What class got a new spec?
What are you even talking about?