I guess people differ because (among other things) of their background. I've played a lot of MMOs (Guild Wars 2 story missions at launch were a real pain) and action oriented RPGs (much faster action than Skyrim), so maybe because of this I had no problem with Norion, Doisha or Gutripper. I also think it depends a lot on your "class" and ability loadout. Doisha with a ranged fighter, especially one who has the Fighter's Guild "Silver Bolt" ability slotted is easy. Same goes for Gutripper.
It also seems you have to keep your gear up-to-date. And as quest rewards do not care about your class and item drops don't happen too often (maybe I was just unlucky), crafting is your best friend. Problem is: Certain professions have difficulties obtaining the materials in the numbers needed (leatherworking was a nightmare ... enough leather to make a set of armor for level 10 ... oh my).
The only quest that I really had a problem with was the one where you infiltrated the Veiled Alliance's headquarters and had to kill 3 bosses ... not much room to maneuver, lots of enemies coming at you at the same time ... I died three times in there.
In general I'd say TESO is another very soloable MMO (as I play at strange hours, I have nothing against that). I remember when you could hardly set foot in front of the big cities in Everquest 2 at launch because all mobs were grouped. But today, WoW, LotRO, Age of Conan, Guild Wars 2, SWTOR ... and TESO are (as far as I can see) very solo-friendly and it should be possible to get to max level without (a lot of) grouping.