Clones' Interactions with Duskblade

I think this would be a bug, not intended, but I'm not sure. It gives so much power to champions with clones it's ridiculous, though. Clones will proc Duskblade's Nightfall passive on an enemy even if the main character's item is on cooldown and will do it without proccing the main cooldown of Duskblade. This means that champions like Shaco, Leblanc, and any clone of anyone created by Yorick can proc Nightfall on 2 enemies or can proc it on a single enemy twice. And if Yorick and Shaco are on the same team, Shaco can build Duskblade proc Nightfall 3 times.