Static groups on the beta server got much higher xp/hour grinding dungeons than Joana’s level-by-level breakdown. Fresh characters leveled to 12 and then did 12-16 in 2.5 hours in RFC grinding group while that level range took Joana over 3 hours. Similar results for WC, SM, etc. Dungeon elites are complete jokes compared to on private servers so melee groups didn’t need a dedicated tank and good caster aoe groups didn’t either if they had one or two skilled frost mages. Random pickup groups won’t be better than questing but if you have a coordinated group of good players it looks like dungeon grinding might be the way to go.
Also layers are going to have high populations and there aren’t dynamic respawns so unless Bliz drastically changes something in the next few weeks open world questing is going to be a pain if you don’t get in front of everybody and stay there.