I agree that Q would be capable of setting up such events, Eg Picards assimilation as you said.
However i disagree that Q is such an evil 'bastard'. Q seems to genuinely like the crew of the enterprise, particularly Picard and Riker. By the end of the episode 'Deja Q' in season 3, Q seems to have developed a real sense of humanity. He admits to feeling ashamed that he wouldn't have tried to save Data's life and above all other places in the universe Q could have gone to live out his mortality, he chose the Enterprise. If i remeber rightly he evens states that Picard is the closest thing he has to a friend in the galaxy.
Perhaps im wrong, perhaps im seeing this in a very one-sided manner being as im a Q fan =]