Personally, I don't have a problem with the quest lines, they are fine the way they are, but the story line should be repaired a bit, it's ridiculous how we always hear the benefits of the death of Arthas in the Forsaken quest lines, and we got back to killing him at level 68. Also Wrathgate event was taken out, because it is in the "past", but it's just like the whole continent aswell.
In my opinion, it would be enough to do just the simpliest changes, like the cataclysm hit the black portal and the seas between northrend and the other continents, and so it is not possible to go there, but we have to go back in time through the Caverns of Time, because the infinite dragonflight killed the heroes who were at the events of Northrend, and we have to do again the events, that happened in the past. It's just an idea though.
I hope there will be some kind of answer, I personally do not long for a full rewamp of quests and others, but would love to see the story line repaired.