I really think that this may not have been as much of a bug as much as a great opportunity for player options in play-style.
It would be great if there was an option that allowed players to designate whether they wanted they champions cone aoe abilities to be detached or not. Champions such as mordekaiser, cho'gath, pantheon, etc. this would be a great tool for those that enjoy the ability to plan their skills around there pathing or have it as a fixed point on the character, or "attached" as it was put.
I may have been only one of a handful of players who enjoyed mord's siphon being detached, but i would really like for there to be the ability to detach such skills.