Reworked Sion (Grievous Wounds on E)?

Now I get that this might not be a necessary addition to our reworked 's kit, but I feel that grievous wounds is a fitting concept for Sion. If I were to add it anywhere, it would be on Sion's E, or "Roar of the Slayer".

My concept would be this:

• "Roar of the Slayer" [also] applies "Mark of the Juggernaut" for 3 seconds to all enemies hit: inflicted units are cursed by Grievous Wounds.
• If lands "Decimating Smash (Q)" on a champion afflicted by "Mark of the Juggernaut", the curse is prolonged for an additional second (on max duration), and the cooldown of Decimating Smash is reduced by 0.5 seconds (up to a cap of -1.5).

Although Sion's E would rarely hit multiple targets in a teamfight, I'm up for suggestions (maybe try -1 second for procing the mark at all) Could this be a viable effect? Even if it's a bad idea, thank you all for reading :)