I don't think it's a surprise to anyone that one of the first clips from the extended Blu-ray version of Suicide Squad has to do with Jared Leto's method acting, since that was by far the most interesting thing about the film.
Leto's justification that he needed to find new things in the Joker so he could give his own spin on the characters is... whatever. Mostly the segment is about how much it attracted him ("That side of me that likes exploration, that likes adventure, that likes to push the envelope, that was set on fire immediately," he says.)
But more interesting is Ayer saying what the set lost and gained by Leto's acting choice:
So during the process of figuring out the Joker and helping Jared create that character, I kinda had to say goodbye to Jared. There was a point when he went away and was replaced slowly and surely by the Joker. It was a fascinating process to watch. There was this really nice guy, a good guy with a lot of depth to him, he's a very thoughtful person … the Joker is not someone you'd say is a really good guy.
Would you say a "really nice, good guy" doesn't make a choice that terrorises his coworkers? I'm not the director and I'm not one of the actors, I don't know. I also wonder how many people on the set knew this is what they'd be in for when they took the job.
Here's the clip, via Collider: