Playing Shadow of War actually makes me want to re-install Arkham Knight...
Is any of the DLCs worth playing?
The season of infamy are just side missions, but for side missions, they each are pretty fun. They are not anything on the level of Cold, Cold Heart from Arkham Origins which felt like a complete, yet shorter-than-a-whole-game standalone story. They have interesting stories though, and get additional "captured" dialogue.
Batgirl felt a bit sparse and overly long for what it was, and offered little new.
Harley Quinn, Red Hood, Robin, Catwoman and Nightwing things are mainly series of challenge maps. I though Robin's was pretty good in that regard, and each character plays different enough (if you're into the finer differences between characters).
The rest are challenge maps which are good if you like combat/predator-focused challenges without any story. And then the skins are cool, but not really worth the price of admission.