Just finished it. If I went with just the main story, it would have been a rather short game.
So for the first 10 hours or so, I decided to do everything. All side missions all activities. That just became boring. So I finished up the factino quests, only one of which was somewhat interesting, with one being an ABSOLUTE chore (Ryujin). After that, did a few temples and then just went through the main story.
A LOT of main story missions are fetch quests. Not only that but you need to go to a guy on a space station to get coordinates for the actual artifact, just adding more of that load screen crap.
The last few missions become more interesting story-wise. One had you jumping from dimension to dimension as you walked through a facility.
The story itself is a bit interesting and I like how they tied NG plus into the actual story. But the overall story and characters are bad. Seriously, you come to the last boss and persuade him to give you the last artifact. His replay is:" OK, but just this time". That sort of thing happens all the time. It's like characters don't really care about anything.
It's just an incredibly underwhelming game and one of Bethesda's worst SP games.