Morello's vs Spirit Visage

for example: 100 AP, 20% CDR, 400 Mana Restores 20% of mana pool on-kill or assist. Applies Grievous Wounds for 8 seconds to targets below 35% of max HP.

500 HP, 55 MR, +200% base health regen, 10% CDR Increases healing by 25%

In a comparative effort, which one of these is more powerful? For healing reduction, a mage building Morello's needs to deal an additional 325 damage against a Spirit Visage user. The SV user has 55 more MR. The caster relies on cooldowns and AP to deal more dps and even at a 1:1 scaling on a skill, the AP only deals 100 more damage, which is then reduced by the MR. The caster gets more casts via the CDR, but drains their cap-boosted pool repeat-casting. If they don't get the kill, they don't get the mana restore, they fizzle out.

This is not accounting for the SV builder's skillset. It's not counting shields or heals. It's the raw stats.

This is not a healthy place for healing reduction counterplay on the mage front. I'm just saying that the 35% conditional is not exactly wrong for the duration it applies, but this item could be the difference in current gameplay issues if it was more reliable. Right now it's current niche effect is as a nuke-booster via the AP. If your burst gets them below 35% HP, it's design makes the damage stick, but now you have cooldowns.

Maybe I'm just babbling crazy, but maybe there is a healthy way to improve this without breaking it.