About 12 hours ago.
The mechanical core of the dragon class concept is well developed, so the class fantasy is relatively easy to produce. The problem I'm seeing is trying to avoid having the Blue dragon spec completely override the Mage class. Chromie HotS can avoid that because her abilities are sand-based, something Mages don't do. A Red dragon spec based on Alexstraza avoids too much conflict with Fire and Destro because it's healing-based.
However, Blue dragons are arcane/frost-based, and I can see that directly competing with Mages. In my 5-spec class concept, I made the spec bow-based, but I don't think Blizzard would go that route, they would go straight Kalecgos mode;
Which is clearly mage-style.