I think Charlie was left in an undesirable position of needing a way to keep the team alive and safe with her sisters in charge, so she went with the only thing she could think of.
(Although once all this is done, is there anything left to do with Charlie? I dunno).
I guess Mallus' group was kind of a Legion of Doom...they had a Green Arrow villain, a Flash villain, a Vixen villain, and a spoiler in Nora.To me the Legion appears in both season 2 and 3, and I thought they were more of an opposing force in season 3. It’s fun to see three dudes take on the Legends but to me it made them feel like less of a threat. Eobard seemed like the true powerhouse in that team and what made it interesting for me was how the other two members didn’t trust him. It would have been cool if Snart had joined the team much earlier and if they had a female villain on the team
I remember people were speculating Thawne would bring Black Siren onto the Legion and Sara would have to deal with her.