If it is like Morrowing where you just roam around at will and you never know what you're gonna get, as Forest would say, then I will pass. I need a direction. Yes, I am a sheep in that regards.
If you followed the main storyline, Morrowind is no different from any other single player RPG. You didn't "have" to roam around. Anyway GW does have a pretty good storyline in the form of missions. There are side quests which don't advance the story and you don't have to do them. The missions come with cut-scenes and your hero/party gets to star in them which is a pretty cool feature for an online game. I would be lying if I said you could solo all the way to the end of the story. Yes, you can have a party of AI characters but they won't cut it for some missions especially near the end. Unless you have a really powerful solo build, you will need to group to get through some parts. This is not a big deal, GW is by far one of the easiest games to find a group quickly. You might change your mind about soloing once you find out how much fun it is to play with other humans in your group.