I do have to agree with you there, Patrick and Chyler's characters were written off in pretty bad ways. They are a fine actor and actress and deserved a hell lot better from the show that put them on the map.
But do I think Patrick and Chyler caused drama behind the scenes? Nope. I think it was something beyond their control, in their lives, that Shonda didn't like. She tried to negotiate with them and it was nonnegotiable and she got pissed off and decided to kill their characters off in the worst way ever.