Yea the person it would make the most sense to have killed Sara would be Merlyn. I just don't know if he coulda left and came back without Thea knowing. I mean making the two groups that want you dead go to war with each other would be smart. Having Ra's and the League declare war on team Arrow. Merly would benefit the most just don't know if he had the opportunity. Also everyone thinks Merlyn is dead right? So Sara wouldn't have been like what are you doing here. Think she woulda been more shocked. Sounded like Ra's was a second father to her so I don't see him doing it. Maybe Talia didn't approve of her sisters relationship with Sara. No matter who did it when news reaches Ra's shes been killed im guessing hes gonna bring hell down upon Star City.