Honestly, it isn't for lane dominance. Lucian and Draven both have very strong laning phases (you can argue which is better) and whatever item they build first isn't because they need it to have a strong lane. With that said, I think its just a case of some players exploring other item build paths and finding one that works well in most cases. Both Twitch and Draven buy Ghostblade not just for its stats, but also for its passive. Last season, Ghostblade did not give as much flat AD, but it did give crit. Both Draven and Twitch were very effective with the item even without the huge flat AD that it has this season because of the active. It gives non mobile ADC champions the ability to self peel, or chase, if things come to that point.
With that said, this season, both Lucian and Draven benefit heavily from the new Ghostblade because of their high AD ratios on each champion's main damage ability, i.e. Lucian passive and q and Draven q. The armor pen makes them hit harder, and the active gives more utility. If you think about the bonus AS from the active, it really does make sense why Lucian would benefit from it. It makes him more mobile, and lets him proc his passive faster as well as hit for more damage.
As far as Ghostblade on Twitch, it isn't a necessary build like it was last season. Infact, unless there are alot of squishies, I typically don't buy it. I find having more flat AS to be better in most scenarios for Twitch, as you don't become too reliant on an active to be effective (i.e. more reliable kiting). Plus, you can already get alot of AD from Fervor and his ult as AD built into it too. I would much rather build more crit, lifesteal, or cc reduction (MS) instead, as he is very very susceptible to cc.
