What the actual fuck are you talking about? lol
Your comparison makes no sense.
Ahri's strength is her mobility. They took out the DFG and took off the DFG like aspect of her charm. Before 6 she isn't even strong in lane since 2 of her 3 abilities can hit minions instead of champs. The speed boost allows her a bit of extra mobility in team fights, and so she isnt' useless in that regard without her ult. You still kill the exact same way.
Nocturne's strength is his sight denial and ganking power as a result of it. He already has a spell shield on his W, gains move speed and ignores unit collision on his Q, and does get that move speed on his E along with being able to zoom 3500 units to a TARGETED champion.
Your comparison is BS.
Would you prefer Ahri got the speed boost after the ball returned to her? That way it'll be like nocturne. That way it will be fair right? So its a flat amount of time instead of based on where you through your ball.
I can barely even comprehend what made you decide to post such a terrible comparison.