Well early S1 tried to setup a B'elanna interest in him that was quickly forgotten, and don't forget Seska and her crazy babydaddy plan.
Seska was good as an evil b**ch. They should have kept her on somehow as recurring. Without her, Voyager also didn't have any Cardassians! One of the things I loved about watching DS9 was seeing what crazy things Dukat was going to do. Seska was kind of like that even though she was in far fewer episodes. Every time you saw her, it was just like "Uh oh...". at least after her true nature was revealed.