The problem us, as Chiquidmaster so succinctly put it, he is optional. His storyline surrounding his father should be way more important to the overall plot than it is. Structurally speaking, I think the game would probably have been better storywise if he, Lae'zel and Shadowheart were actually mandatory. Based on the amount of focus their storyline could reasonably get in each act, having them as characters the writers knew would be there in any playthrough would have made them (especially Wyll) better written and made the story feel more anchored. Imagine if in Dragon Age Origins you could have killed Alistair and Morrigan. They each have major moments in the game that are vital to the progress of rhe story and carry real weight potentially. How would it have gone if the writers had to account for either not being there?
Imagine a version of the story where Wyll's connections to the city allowed you access to certain places, or opened the door to plot lines. Imagine if trying to save his father was one of the major throughlines of act 3, with that being how you were going to overcome Gortash somehow. Those are options you don't get if the writers can't rely on the character's presence.
