I really like this rune. The 4 horseman theme and its applications are excellent. However, objectively it cannot hold a candle to Rune of the Fallen Crusader and that is disappointing. It would not take much to have it on par either. Here is an idea
Current version vs Possible
Damage↑ : 1% to 5%
Healing ↓ : 1% to 5%
Slow : 15% negligible compared to what we have access to, but could function better as a small speed increase or leech. Maybe 2-5% even if only for minions.
Damage↓ : 2% to 3-5%
I believe these changes would make this rune compete with Fallen Crusader.
Hate to see the devs waste such a cool concept because of this lack of insight.