IMO for the most part the new quests are great, the amount of non-intentional training isn't though. I guess it will get better as less people are doing the quests at the same time. Worst places for this seem to be around the 255 incarnator where training directly interferes with regular sk. Also pretty bad around the portal into inferno.
The quest mobs themselves are rarely the problem its the Mortiigs/Heckers etc that go with them.