Siggurdsson should be getting at least 8+ goals for you. In theory, if you can score goals in a Swansea team, you should be doing even better in an Everton team with better players around you. Doesn't quite work like that though I guess. Not sure if he only looks quality when he's the 'main man' (Like he was at Swansea) but for the money you paid, he has to score more. He's deadly from inside 30 yards with his long rate shooting and takes great set pieces, needs to do this for you consistently to justify his price tag.
It's not even goals that made him a stand-out performer last year, it was his assists. Hasn't looked anywhere near that level so far, early days though.