I wouldn't say he's obsessed with John. We haven't had a big scene with John, since just after she helped capture Fitzgerald and Mr Smith, which was about 2 years ago. After that he didn't appear again for over 5 days, when he was there to help Anna bring Andrew home from hospital. He next appeared on Tuesday night, when he had relatively short sex scene with Anna, whilst Andrew slept beside them, and then the following evening he gave Anna a foot massage. So three relatively minor scenes in an 11 day period, is hardly evidence of obsession?
Over the same time period, Rebecca and Andrew have both appeared in 7 scenes, Madison in 6 scenes, Jeremy, Benjamin and Timothy in 5 scenes and Emily, Mr Burnsfield and Michael in 4 scenes. Alfred and Schmitt have appeared in the same number, but both have at least one very big scene. So 11 characters, that the Dev is apparently more 'obsessed' with besides Anna.
If anything we're due a meatier scene with John, but it doesn't look like we're going to get one in the near future.