Perhaps Duskblade ISN'T the problem, but lethality(or serrated dirk)?
You recently(actually a while back but) buffed lethality work in the reverse of how it used to. You get more earlier, and it works based on your level. Now people who are getting behind are still fine because they have the same or more lethality than they did previously. Perhaps you should target serrated dirk, and give it less lethality than before. From my experience serrated dirk is an AD assassin's powerspike, and is much more powerful than other half item power spikes. Killing them in lane, pushing the wave so they lose the experience, and coming back doesn't feel very good when you have a Zed on the other team who, after completing serrated dirk still has an advantage in that he can nearly one shot you with a W>E>Q+electrocute proc(Which electrocute may be the problem, it is a lot of damage).