Everyone's so quick to jump on the editing being an issue here.
Could Leto's overall performance have been the victim of poor editing? Sure. But I'd say these are just as likely.
1) The scenes left on the editing floor contributed nothing to the plot, even moreso than what was actually left in. Frankly, his involvement in the film just barely services the plot as is. The Joker could have been written out of the film completely with little-to-no consequence. What does one extra second of him slapping Harley or him convincing Monster T to kill himself (LOL) really contribute, besides more screentime for the sake of it?
2) The cut Joker footage simply wasn't any good (per test audiences), and Ayer picked the material that was actually serviceable. As much as people may not want to admit this, it could have simply been a bad performance all around, and what we see in the film (both the theatrical and extended cuts) is the best of what they had.
Ultimately, the script was more at fault than the editing methinks, because Leto was given the task of playing a character that really had no business being in the film as written. And I think Ayer realized that in the editing room. They shot all this Joker footage, only to cut the movie together and realize it didn't do **** for the plot at all. I actually think cutting the Joker down to a minimum was the smartest editing choice they could have made, from a narrative perspective. Cutting excess fat is responsible filmmaking. Here's the problem:
- The Joker is still completely inconsequential to the plot, even with the screentime he had left.
- WB marketed the **** out of the character.
- Everybody talked up how wild and crazy Leto was on set.
- Leto seemed largely aimless in the role, aggravated further by the weird psychedelic filter they used to highlight teh crazy.
So yeah. Poor scripting decisions that the director should have caught early on, misleading marketing, and an actor who felt like he was experimenting and improvising rather than delivering a performance. Those are the big culprits.
Having said all that, there could be five minutes of Joker footage left on the cutting room floor. There could be fifty minutes. Either way, I don't believe for one second that a great Joker performance exists somewhere in the editing rooms at WB. Even if they had restored all of Leto's footage, I figure it'd have simply been more of what we've already seen. And honestly, based on what we've seen, I'm glad they saw fit to spare us.