I honestly can't believe that Oliver was completely broken down in three weeks because of League of Assassins brainwashing and some herbs. I think he is playing the part of Heir to the demon for now, so that he can learn under Ra's Al Ghul until it is his time to strike, because "only the student has hope of defeating the master". My little proof that Oliver might be faking, is in the following promo:
Unfortunately, I can't show the video here, for some reason. So this is the link: http://www.spoilersguide.com/arrow/season-3-episode-22-this-is-your-sword-canadian-promo/
In the promo, at around 3 seconds in, it shows Oliver talking like his normal self to what appears to be Maseo. He says they need help and it makes me think that they are working to together to bring down Ra's. It then cuts to a video of Tatsu in her katana uniform. So it makes me think that they tell Tatsu to join the team, as Team Arrow fights the League of Assassins.
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