Characters in comic books tend to go through phases and changes. Sure, the rough idea of the character might be the same, but there's a lot of specifics that can change. As such, HeroClix figures will come in different versions to show off these different types of character changes. So while there's already been a different Joker previewed for the Joker's Wild set, that doesn't mean that's the only Joker in said set.
This Joker is a lot more robust than the previous one. Lots more special abilities, too. And, of course, as you'd expect, a higher cost to play. He's got a couple always-available special abilities in the form of being able to use Poison (and that damage being penetrating damage) as well as being immune to Precision Strike. As for his dial, well, it's never quite the same thing twice. He switches back and forth between a couple abilities on each click, with those changing up all the time. This is definitely the "unpredictable" Joker.