Suggestion for the New Keystone

What if it worked more like the old Fervor? (Details ahead)

for example: Damaging enemy champions grants you stacking bonus AD (max 5 stacks) for 8 seconds (each time you deal damage the 8 seconds resets). Upon reaching maximum stacks, convert 5-10% (based on level) of damage dealt to champions as true damage for 4 seconds. Melee Only: Damaging an enemy champion refreshes the 4 second duration. Once it falls off, the second part has a cooldown of 20 seconds. You can still gain the bonus AD during that time, but the true damage will not trigger until the cooldown has ended.

Bonus AD: Max 10-60 based on level:

Bonus AD per Stack: Lvl 1: +2 per stack Lvl 3: +4 per stack Lvl 6: +6 per stack Lvl 9: +8 per stack lvl 12: +10 per stack lvl 15+: +12 per stack

% Damage converted to True Damage: Lvl 1: 5% lvl 3: 6% lvl 5: 7% lvl 7: 8% lvl 9: 9% Lvl 11+: 10%

I think this would make the play patter feel a lot better and would make it much less abusable by other classes like tanks....

In its current form, my fear is Maokai auto attacking a few minions, then once its ready to proc, point and Click W's onto me, AA/Q, throw sapling, AA walk away. Converting 20% of all his base damages (which are high) to true damage.

This is just me though. Thoughts?