I don't know the validity to the reason behind the reshoots. Movies have done them, and they can and can't work. That being said, the bar scene could have easily been a reshoot since there were no FX there and it was just dialogue.
According to Jai, the reshoots are to add more action:
Jai Courtney, who plays Boomerang in the film, tells Entertainment Tonight that comedy had nothing to do with it.
I wouldnt say were going back to make it funnier, he says of the newly shot sequences. Theres some additional action stuff that weve been doing, which is pretty dope. Yeah, really, were just kind of adding in that sense.
When the ET reporter reiterates that shed read that the new scenes were designed to add more jokes that match the tone of the initial, well-received Suicide Squad trailer, Courtney simply says: You cant believe everything you read.
https://www.yahoo.com/movies/jai-courtney-on-suicide-squad-reshoots-you-152122502.html
The humour has been there from the first trailer, but the last two have more, that's all. With characters like Harley and the Joker, the humour was always going to be there no matter what. The three trailers have been good, I prefer the first two though.
What happened to the people whining about the tattoos? Nothing to say anymore? They love everything Ayer is doing now?

t:
The movie should get decent reviews because it should be fun enough for shallow critics, but some of David Ayer's movies have bad reviews:
Sabotage RT 19%
Street Kings RT 36%
There are no guarantees, but if I like the movie, that's what matters to me, I don't care about critics that seem to think all these movies should have the same tone or forced, dumb juvenile humour to work. Nolan was lucky they didn't care back then, Tim Burton was not so lucky with Batman Returns:
Batman Returns received a lot of controversy for being too dark and received a PG-13 rating for brooding, dark violence by the MPAA.
The initially negative reaction to Batman Returns, however, prompted Warner Brothers to re-think their approach to the franchise, and the series was handed to director Joel Schumacher, who adopted a much more lighthearted and camp approach to the characters. However, the generally very negative critical and fan reaction to the Joel Schumacher films in the franchise, particularly 1997's Batman & Robin, sparked a critical re-evaluation of Tim Burton's dark, gloomy and expressionistic first sequel in the franchise.
http://batman.wikia.com/wiki/Batman_Returns
So, now dark is out again and fun is in... till critics change their minds again!! That's how people work, they just get tired of one thing after a while, it doesn't matter how good or not the object actually is. People are fickle!
