Writing for Cheetsheet.com Nick Cannata-Bowman has an article posing the question "Is DC's 'Legends of Tomorrow' Hurting Other Superhero Shows?"
In it, he wonders if Arrow and The Flash, being used to set up Legends of Tomorrow, are not able to tell their own stories. I've seen this complaint before and heard it on podcasts, most recently an episode of Flash TV Talk. I would argue that Legends of Tomorrow is not hurting the other shows, but enriching them.
I'm going to talk about some of the specific characters, so...
Spoiler Warnings for Arrow and Flash
Sara was a major player in Season 2 of Arrow. I remember being a little leary about her character, because everyone knew that according to the comics it should have been Laurel running around as Black Canary. She became an integral part of the show, in both the present and past storylines and one that I really grew to enjoy. I was genuinelly saddend by her death at the end of episode 301 and felt that the storylines surrounding her death, both the grief of the other characters and the search for her killer, were given their proper due. After the introduciton of the Lazarus Pit, many, myself included, were surprised that it wasn't used to bring Oliver back from his own death, but it makes total sense for Laurel to use it to bring back her sister. It's important to remember that Sara had been a member of the League of Assasins prior to showing back up in Starling City in season 2. Sara and her importance has been felt since the first episode of the series, and to me, her return this season has been handled well. It shouldn't be something that is told in a one and done. Without naming names for fear of giving spoilers, another show that I watch recently dealt with a character who was missing, and despite the even greater odds, she was both located and retrieved in the span of a single episode. I wouldn't want that to be the case with Sara. In fact, I think it could be aruged that Sara's return could be playing out exactly as it has so far without Legends of Tomorrow at all. She's too important to the Arrow show.
While I agree that season 3 of Arrow did have to work extra hard to include Ray Palmer/The Atom, I don't think that has anything to do with Legends of Tomorrow. I think it has more to do with the fact that originally he was supposed to be Ted Kord/Blue Beetle. Looking at Ray's development, to me it's clear that he was developed first as a different character. Keep him as Ted Kord, and I think he loses a lot of that feeling of "going out of their way to introduce him." I think it makes lots of sense for Felicity to have this subplot devoted to the search for Ray. Of all the other characters, she was by far the one Ray was closest to and even though their romantic relationship is no more, I would be shocked if it wasn't Felicity driving this subplot forward. I would also argue that there hasn't been much time at all devoted to it. She mentions some computer and phone problems in one episode, debates whether or not to listen to Ray's message from "beyond the grave" and finally does. This all spans over the course of a few episodes, but each episode only devoted a handful of screen time to it. Like Sara, I think this storyline could be playing out exactly the same regardless of the status of Legends of Tomorrow. No, I don't know that they would be bringing Ray back if not for Legends, but at this point in the show it makes perfect, in-story, sense.
Leanoard Snart has long been portrayed in the comics as a character who is mostly out for himself, but one that was willing to serve the greater good so long as it served himself at the same time. He isn't, and never has been, "evil" for evil's sake. In the show, he has without a doubt done villainous things like when he killed a man in the theatre in his first appearance in season 1. But he has also shown not to be without his own code of honor, and doesn't go around murdering people just to do it. In fact in his latest appearance his motives were entirely an attempt to save his sister's life. No, he's not a hero, but he is willing to do heroic things and I think that fits with his established history. I imagine being a "villain" will provide some friction between him and the rest of the Legends group. His character has been a fan favorite on the show, why wouldn't they use him more often?
Like Sara, the prescense of Ronnie Raymond has always been felt, if not seen, since the first episode of The Flash. As the signficant other to one of the show's primary characters, I wasn't at all surprised to see significant time given to his character last season. When the Ronnie half of Firestorm was "killed" stopping the singularity over Central City, we knew he was being replaced by Jay Jackson. This is possibly first time I think Legends of Tomorrow is possibly be driving The Flash. It has been speculated that Robbie Amell (the actor behind Ronnie Raymond) is not on Legends of Tomorrow due to contract issues or because he is going to be appearing on the new X-Files revival. But the producers understandably wanted Victor Garber, the actor behind the other half of Firestorm, to continue on the show. Luckily, in the comics there is an established history for different people hosting the firestorm matrix, so this was a relatively easy fix, and when they decide to find a new Firestorm to save the life of Martin Stein (Garber) it makes complete sense. Personally, as a fan of Robbie Amell's, I'm hoping to find out that Ronnie has been stuck on Earth 2 and that we get even more screen time devoted to his story.
Kendra Saunders is another character that is going to be set up for Legends of Tomorrow. This is also the first character that I will without a doubt concede is only appearing because of Legends. She appeared in the season 1 finale as part of a montage and was on screen for maybe three seconds. In season 2 she has had a few minutes of screen time, and so far is merely the cashier at Jitters and a potential love interest for Cisco. I don't believe we would be getting her if not for Legends, but it's too early to decide if she is an assett or hindrance to the show.
Now, I personally am a huge fan of both The Flash and Arrow, and of crossovers in general. I loved seeing John Constantine in the latest episode of Arrow, and hope we see him again. I am really hoping to see him show up on Legends of Tomorrow. I do understand why someone who is only a fan of one show or the other may not like the direction they are moving. But like it or not the shows are being set up as one overall story (something frequently done in the comics as well).
I'll leave it with this quote from Stephen Amell, reported on by ComicBook.com, and something that made me very happy to see.
"It's basically one show," Amell said of Legends of Tomorrow, The Flash, and Arrow. "The universe now, as it exists, is basically one show."