I'd like to keep this short. There aren't a lot of thing that are worth mentioning in this episode, but there are still spoilers, so fly a way like a dragon, but not Diaz, if you haven't seen this episode yet.
Episodes that have very little Oliver in them tend to suck. This episode had only one scene with Oliver that was, out of all things, an Olicity scene. And despite that, this episode defied all odds and didn't suck...it just wasn't very good. I think that proves that Ricardo Diaz is a good enough villain to hold an episode on his shouders but I think he will be better when he interacts with the main character.
Now, what did I like in the episode? Well, Diaz's backstory. I think they did a great job of making us belive that this man has gone trough some bad stuff and is broken from the inside. I also like the dynamic between him and Laurel. There were some fight scenes that weren't anything special, but they were very bloody. Bloodier that usual. That made Dragon seem like a more threatening villain, but then he kinda said "I can't do anything myself, but my hot bodyguard can! Ha ha!" which made him less threatening, but then he totaly outsmarted those Quadrant guys, so he felt threatening again. I don't know. I still gotta see a little more of him before I deside whether or not I like him as a villain.
There was also a pintless, stupid, Helix Dynamics sub-plot and that was bad. It was a waste of a good 5-10 minutes and could've been given to Oliver, but the writers just love to put Felicity in the spotlight. The main plot had some interesting parts, as I mentioned above, but was ultimately kinda boring and felt really pointless at some parts. I think a lot of scenes were wasted in this episode. Whoever, Felicity's whole problem kinda made sense and could've been handled way better. And I don't like that Curtis and Felicity are talking and working togheter again because it makes that whole storyline with the Civil War worthless. He just showed up to her place without any explaination when did they deside that they are cool again.
So overall, this episode was interesting, with some good character development for Ricardo Diaz, but ultimately sorta boring and at moments - really pointless.