Starfleet's relationship with the Cardassians was established in TNG, and I think that DS9 failed to reiterate that properly in the first season.

Then you have Obrian's history with the Cardassians - quite significant for his new assignment and without this context the character feels like a fake tough guy. The acting and directing was brilliant, because we could feel the restrain, but without understanding this it comes off cocky. It's like watching Travolta's character dance poorly in Pulp Fiction - if you didn't know who Travolta was, the scene comes off poorly acted. Or Robin Williams playing a gay man playing straight. Some background of the character is important to actually enjoy the acting mastery that we are witnessing.