Nocturne W change

I believe that if Sivir's spell shield cost 0 mana then Nocturne's Shroud of darkness should cost 0 mana. The only difference between the 2 is that one gives mana back and the other doubles the passive attack speed the skill gives.

Sivir's spell shield is a lot more handy to use then Nocturne's because that extra mana gained could mean life or death for her or her team. At level 1, if a spell is blocked, sivir gains 80 mana; that is 10 more mana then her main damage dealer (her Q) it is also 20 mana less than her ultimate at level 1.

Nocturne's Shroud of Darkness is handy for duels i guess but it never really feels that it helps at all. At level 1, if a spell is blocked, Nocturne gains 40% Attack speed for 5 seconds. That is cool i guess but it's really only for duels and nowadays most duels last more than 5 seconds with the raise of Cinderhulk jungle and tank comps.

Maybe 0 mana may not be the answer but a change if anything is needed for his W. Please feel free to respond with any suggestions you guys may have!