Paul Weaver wrote:
Most of DS9 season 4 seemed to be written without any idea that Worf was around, perhaps the scripts were outlined before they know Worf was joining, perhaps the writers didn't have any idea. Once Season 5 started, with his interactions with Dax and Martok expanding on the tenuous link with OBrien, Worf became much better.
I think that they purposely downplayed Worf in season 4 becaause they didn't want DS9 to suddenly become the Worf show. On Voyager when they added Seven of Nine she dominated the show and I think the DS9 crew didn't want that happening on DS9.