Suggestion for Dark Harvest and Tweaking it's high damage

EDIT: This video is from PBE, didn't know until I checked the date of the video. Can't delete the link.

It is preseason and with the new masteries, we have yet to fully comprehend what is too weak or strong. Looking at this, it would seem Dark Harvest is incredibly strong. This is my first idea, add to the description of Dark Harvest:

The damage of Dark Harvest down scales depending on the % of max health the enemy champion would lose from other sources of damage from that same attack. When the damage applied by Dark Harvest would increase the % of maximum health to above 45%, it will instead downscale so that it only does that much damage.

Even at this amount, enemy champions can be three shot by basic attacks, and this is before 3 crit items. Even like this, it's still hard damage. This was my second idea:

Your next attack on a champion or structure or structure consumes Soul Charged to apply a mark, dealing a third of it's damage immediately. Every 3 seconds you remain in combat with them another third of the damage is dealt, lasting up to 8 seconds before the mark is consumed. Timer pauses after 2.5 seconds out of combat with them.

I personally like this one more, because it would be very good on immobile carries like or whom can't get away from an assassin, so they stall the timer to set off all the Soul Charged damage with their ult cc and range. It keeps the damage so it's still relevant against other squishy carries unlike the first suggestion, but gives a significant enough amount of time to react to it. Is there any better idea, and if so, please state it.