Thor often gets dumbed down and/or powered down in the pages of the Avengers to make the rest of the team relevant. If he were to face some of the menaces the Avengers face in his solo book, he would be able to take care of business by himself.
Justice I thought was a well done example of a character being less effective, since it was an ongoing subplot with Justice. By the end of his tenure with the team he had smartened up and gotten past his hero worship.
Personally he is one of my all time least favorite characters in the history of fiction. He oscillates between being a vain immature prankster brat to a vain condescending arrogant ass who throws his years of experience in everyone else's face. The years of him being with Ben's girlfriend ruined my opinion of him and the Lyja retcon made things even worse (at least with Alicia he matured to a point even if he was as boring as drying paint).
He needs to be a solo adventurer for a few years and cut the cord between him and Susan and Reed. They treat him like he's another one of their children and for almost 50 years he's enjoyed the attention and never stepped up and became his own man. He will always be overshadowed by the others.
I want to see the Fantastic Four replace Johnny for a good five or so years. Let Johnny have his own life without his big sister.