I feel Darius would be more balanced if his W didn't have a scaling mana cost

It gets up higher and higher at each rank, starting from 30 and ending at 50(if memory serves correct).

When Darius is in an extended duel, spamming a 50 mana cost spell about 5 times is huge on him, and with his low mana pool, this is killer.

What I propose is that his W start at 35 or 40 mana cost at rank 1 and STAY that way for the entire game.

Basically, only costing 35 or 40 mana at all stages of his W having a point in it, for balance purposes and so he doesn't run oom spamming it in a super extended duel(which is rare nowadays).

Thoughts?