I just want to take a minute to recognize how frustrated Cassidy must be with the writing and writing staff. This is how I imagine their conversations going:
Arrow Writers: Welcome aboard, Katie. This character is great. She's based off of Dinah Laurel Lance, who in the comics is this mega badass female vigilante named Black Canary. She's actually one of the strongest fighters in the comic universe. She kicks loads of ass.
Katie: Oh, wow, that sounds really cool.
Arrow Writers: I know, right? Well, in this show you'll be a lawyer and most of your storylines will be about a melodramatic love triangle.
Katie: ...but you just said...
Arrow Writers: Don't worry. You'll have plenty of moments where you're a badass. Like this one time you try to fend off this assassin with a shotgun. You look so cool.
Katie: All right, now that sounds go-
Arrow Writers: Then your gun immediately jams.
Katie: ...
Arrow Writers: This other time you punch this dude who's trying to kidnap you.
Katie: Awww yeaa-
Arrow Writers: Then you're immediately tasered and knocked out and kidnapped.
Katie: ...
Arrow Writers: Then this other time where you disarm one of the many armed men who walk into your dinner party.
Katie: Let me guess. Another gun is immediately stuck in my face and I look like a reckless dumbass.
Arrow Writers: How'd you guess...? Never mind. Now your biggest moment comes in the finale. It's huge. There's this big earthquake, and all the characters are telling you to get to safety. You disregard them and you run into a collapsing building to get some work files and end up getting your ex-boyfriend killed.
Katie: ...Am I being punk'd? Is Laurel the most elaborate punk'd episode of all time?
-season 2-
Arrow Writers: OK, Katie, we recognize we made a few mistakes with your character. But don't worry. It's a new season. We're improving all the characters. It's time for change. It's time for Laurel 2.0.
Katie: I like the sound of this.
Arrow Writers: We're going to make Laurel irrationally hate the hero of the show and blame him for Tommy's death. She's going to want to catch the vigilante. She gets obsessed. She becomes a somewhat interesting antagonist.
Katie: People are going to hate Laurel even more, but at least it gives her something to do besides be a love interest. Fine.
Arrow Writers: Then two episodes later we abandon that plot thread.
Katie: ...
Arrow Writers: But don't worry. We have a huge fix for your character coming. It's going to fix everything.
Katie: Thank god.
Arrow Writers: So you know how when we announced this show everyone expected Laurel to be this awesome kickass sexy vigilante Black Canary that people would like? Well, we're going to bring in ANOTHER character who's this awesome sexy mega badass vigilante Black Canary. She's going to be a big character, having flashbacks and character development and the whole shebang. She even has a sidekick!
Katie: OK. How does that help Laurel?
Arrow Writers: Well, we're eventually going to kill off that character and Laurel will take her place.
Katie: ...but if people really like that character, won't that make people hate Laurel even more? And besides that, aren't you setting up a standard that Laurel can never live up to? Oliver went through five years of hell to become what he is. Sara was trained by assassins for five or six years. Laurel... took some self defense classes? Won't Laurel just feel like a lame wannabe when she becomes a vigilante? A cheap replacement?
Arrow Writers: Huh... We didn't really think of that stuff...
Katie: You god damn sons of bitches.
-some new scripts come in-
Arrow Writers: OK, it's time for Laurel 5.0.
Katie: I thought we were doing Laurel 2.0...?
Arrow Writers: No one's perfect. We screwed up a bit. But it's a new day. These are new scripts. This is a new Laurel. We finally found the perfect storyline for her.
Katie: Oh boy...
Arrow Writers: So while Laurel's sister is going around town as a badass vigilante helping the hero fight bad guys, getting character development, being in flashbacks, Laurel becomes a pill popping drunk.
Katie: ...
Arrow Writers: She actually gets pulled over for drunk driving, she pulls the "DO YOU KNOW WHO I AM?!" card, and the cop lets her go because her dad's a cop. Oh, and she goes on a date with the guy who wants to put Oliver's mother on death row.
Katie: ............................
Arrow Writers: Oh! One great upcoming story we forgot. Laurel joins the prosecuting team that's working to put Moira to death.
Katie: FUUUUUUUUUUCK YOOOOOOOOUUUUUUUUUU!!!!!