I feel like the drop of quality for me happened when they made George repeat his intern year. He was never my favorite character, but the way TR potrayed him was unwatachble. His acting was so bad in season 4 I was happy when they started phasing him out in season 5. Of course his acting improved in the second half of season 5. Another thing, rewatching the show they really have ruined Arizona's character the last couple of seasons. In season 5 and 6 she is so likeable and dare I say professional? The Callie/Arizona/Mark might of been the second drop in quality for me after making George repeating his intern year.