Well, I took a break from this forum since I wanted to work on some other stuff. Took a break from every forum, actually. Now the show is back on, and thus I return.
Firstly: the way they handled the Olicity issue here is, IMO, the writers and showrunners speaking to the people who do the "Olicity *heartshape*" trolling on social media, and if that is the case, BRAVO! I know that Felicity will probably be together with Oliver at some point, but there's none of this whole 'OTP' stuff in Arrow despite what some would hope (regardless of pairing).
Secondly: In a way, they handled the final moments for Sara very well. We all knew it would eventually come, but I would have kept her around if only to see if Laurel worked out as a successor. We don't know if she will, so I'm (for once) hoping that they are going to have Ra's with a Lazarus Pit, just in case.
As for Sara's killer: It could've been Ra's, Komodo, or Merlyn, as far as I'm concerned, but take note of something. When she turned, she asked whoever it was what they were doing there. She knew them, and what's more, she trusted them, because her expression after she receives the first arrow is one of betrayal.