Riot, as someone who plays Quinn a lot...
She's my 3rd most played champion. Nerfing Duskblade is going to hurt her a lot, especially by that much. Quinn has been pretty much forced into being a ranged assassin, and these recent nerfs to one of her core items will make her a lot less viable.
Is it an unhealthy item? yeah, I think it is. Maybe Buff Quinn more? Those buffs on PBE are more quality of life changes than anything else.
Hell maybe even rework Quinn again... I don't know. All I know is that this nerf is going to make her worse.