To all the people that said that the film would have been better if the group was just sent to take on the Joker (perhaps after he takes over Arkham or something), I wholeheartedly agree. No one in the Squad aside from El Diablo (and maybe Katana, who you could completely excise from the script and not lose anything) really has any abilities that would make them fit for taking on a supernatural entity. Deadshot has guns. Flag has guns. Harley has a gun, a bat and some gymnastics moves. Croc is stronger than your average human and can swim like a fish, but he's not really super-powered. Boomerang throws Boomerangs. These aren't the people you send against a supervillain of that kind. But sending them against a supervillain with a large criminal network like the Joker makes sense. Especially considering Harley is there. It really never made much sense to have her on the team to begin with; she's batsh** crazy and yeah, she's a dangerous hand-to-hand combatant, but how she got that way is never really all that clear. Maybe she was a gymnast and a martial artist her who life, but it didn't look like she was much of a fighter when the Joker's thugs took over Arkham and attacked her. So somehow she gained these amazing fighting abilities from hanging around the Joker for a few years? Maybe, but it seems a little flaky. However, having her on the team to get intel in taking down the Joker WOULD make sense. And while she wouldn't want to betray Mr. J, she may go along with it simply because it means she gets to see him again.
Anyway, just thought I'd get that out. But sadly, WB seems to think that in this DC shared universe, there needs to be a ton of CGI and death to make a movie good.