I leveled really slow, it took me maybe 3 weeks of just doing Summerset quests, dailies and dungeons, I have not done many quests outside Summerset zone.
I did, however, do Harborage quest and am in Coldharbour, but that zone is massive. Is there a good reward for finishing the main questline? Otherwise I won't bother.
Currently in Orsinium since I read about Proving Grounds and it seems interesting.
Anything in Morrowind zone worth doing?