Finally watched the finale. Ras gave ole that work.
I'm not sure if yaw discussed this, but what was merlyn's reason for killing Sara? He thought Ollie would kill ras?
Sara was on assignment to hunt down Merlyn for the League. Basically that was it.
But Merlyn staged it so it would any blood debt was made be washed away through Ollie. He knew damn well that Ollie was no match for Ra's, Ollie is technically no match for Merlyn and Merlyn FEARS Ra's which was why he backed away when Moria threatened him that she was gonna hit up Ra's if he would ever try to get Thea. Merlyn basically already plotted to use Thea as a pawn to clean his slate the moment he learned Thea was his daughter. That's arguably why he even got Moria out of prison thinking he can get in close until Moria pulled that Ra's card.
So, whomever was assigned to go after him and kill him, he was going to have Thea on deck to kill any assassin first. It just so happened to be Sara, which can be argued is due to Sara knowing Merlyn personally and was from Starling City. She, it can be reasoned why she INITIALLY came to Starling the 1st time around before going rogue. She stated she returned due to the undertaking which was Merlyn's doing and the very reason why Ra's is hunting for him. So, she could of been originally on assignment before going rogue.