Joker is a side stepping hard to hit figure with Indom, poison and bat enemy. Packing leadership means if you pull a big gotham baddy like freeze or clayface you can work for that too.
Also I might be wrong, but new underworld carries based on keyword right? So sidestep and carrying can be huge for positioning.

Ran a team with Talia, Christmas Joker, Batman Beyond, and a couple of other pieces and with those three pieces alone had Outwit, Perplex, and Prob Control covered. They tore up their opponents - most notably title character Batman.

The rare Joker is the only rare I used between two pre-release events, but he more than pulled his weight, thanks to the being next to impossible to hit, as well as the Leadership. Didn't have any Suited Henchmen with him, but they weren't needed, since I had Zatanna to provide Bat bystanders for Mastermind fodder in one of the two events.

Played against John Stewart twice, and he pulled his weight.

very nice, I really like this set