"A linear approach to quests"? The Kagha storyline has at least a dozen possible resolutions. There are almost as many ways to deal with the Hag. With Minthara, you can just kill her, side with her and attack the Grove, decline her offer, pretend to side with her and betray her at the Grove ... There are even multiple outcomes for Barth's stolen amulet quest.
If by linearity you mean the game forces you to do things in a particular order, yes, it does, once, in that you have to battle the goblins outside the Druid grove before you can explore beyond. Once you've done that, you can literally go anywhere and take on any quest or battle you choose. This is one of the most open and least linear games I've ever played. The only limitations on freedom are your own style of gameplay. Experiment, and ye shall find.
