The real winners of Duskblade of Draktharr...

Are high-damage bruisers with burst potential.

Think a J4 or a Wukong with 2 and a half offensive items almost deleting your adc is annoying? Well now Duskblade will make it even easier. Knock knock. Hello? Surprise bitch, it's Hecarim, with more damage added to his already insane upfront burst. And free movespeed is always a pleasure. Everyone's favorite lee sin also gets a new toy to extend his burst later so maybe he isn't useless past 25 minutes anymore. But it's pretty pricey so cheap options like hexdrinker will still be more attractive along with the usual warrior enchant into tank build. Xin can easily get his Q autos off before the mark proc's around midgame (where you'd probably have the item by then), plus the W crit.

Pretty much anyone with good damages that builds like one or two AD items and a cleaver is probably gonna be really happy.

Aside from those bruisers, I think Kha'Zix also will like this item, as it'll improve his non-isolated burst and make his target selection much less restrictive in later fights.