IS AN ASSASSIN
No other AD carry would build duskblade because that requires building more armor pen. ADCs don't usually wanna build armor pen and build crit. However now that armor pen is more balanced ADCs should have the diversity to build it if they want and fall off properly/not snowball insanely.
Also do you really want to fuck ADCs over? Do you know how these boards work? They whine and complain about whatever class is weak. Morde's weak and getting "nerfed"? 5 threads about Rylais. Beginning of season 6, everyone complaining ADCs are too weak? 5 threads on ADCs/Last Whisper. Besides, you're saying fuck ADCs yet we complain about Kalista being weak and no other ADC than Quinn would build Duskblade.
This kind of mentality of "well this X is strong so FUCK THEM and lets NERF THEM INTO THE GROUND AND NEVER BE GOOD FOR MONTHS" is the stupidest thing I see. What about those mains? Was it really fair to Jax mains for Jax to be completely gutted just because "he was strong at time." (48% winrate top lane, 52% jungle.) No, it wasn't. Neither is it fair to Quinn to be nerfed for no reason.