In quest design I'm not agree with you. Quests are generally fun and include some twists and turns to make things interesting. There're also woven into the gameworld nicely. For example you think it's a simple kill and fetch quest. But while pursuing that quest, you see that truth is totally different. Apart from a few, the quests don't present the player choice but also there're few simple kill that, fetch me that quests with no story behind it. Quest dialogues are well written, but unfortunately they suffer from mediocre translation and voice acting.
I think you´re talking more about writing and presentation than about design.
I´d agree they did a solid job at differentiating side quests from each other story-wise (though I found most of the quests unremarkable in this aspect still), but design-wise, there aren´t many quests with choices and different outcomes, quests with multiple ways throughout or multiple entry points, or quests which require some non-hand held work from player.
This wouldn´t be much of a problem in an exploration driven game like Morrowind, where a simple "bring me a dwemer tube from a ruin" quest very likely results in player discovering many other points of interest with something else to do and find, or even finding the tube in entirely different location, but in Two Worlds 2 all that exploration nets you are locked doors, generic hostile camps or utterly generic dungeons with generic random level scaled loot if you´re lucky. As a result, Two Worlds 2 is very strongly a quest driven affair and given that, quality of its quests simply isn´t sufficient in my opinion.
As I see it, strictly design-wise, the quests are repetitive, majority of them take 10-15 minutes to finish and doing so very likely constitutes most of the playtime (at least once one realizes how pointless exploration in this game is).
As a side note, the game is kinda deceptive in these matters, because the eastern half of the savannah island initially shows a promise of meaningful exploration and quest design around getting a pass is more elaborate than pretty much everything after that.
For the record, I did enjoy most of the game´s mechanics and how smoothly it played which is likely the reason I managed to finish it.
As for the expansion, I thought one of the goals of it was supposed to be fixing the original game´s dismal exploration aspect to some extent (I still have to laugh how utterly meaningless the boat is, even though I rather liked the mechanics of it), but since instead of being integrated into the main campaign it plays as a standalone, obviously my assumption was wrong.
I think it´s a pity, because imo the game was in a desperate need of an add-in á la NotR.