Turn keystone Lethal Tempo into anti-health shredder
1.5 seconds after dealing damage to enemy champions you gain 30-60% attack speed and your basic attacks does X% target max health as bonus adaptive damage for 3 seconds. Basic attacks extend the duraiton up to 6 seconds
Alternative
Basic attacks against enemy champions grands 10% – 20% attack speed which stacks up to 40 – 80% attack speed based on level which also increases the attack speed limit by the same amount. At max stacks your basic attacks does bonus adaptive damage equals X% target max health
The reason that it should do bonus damage is because I don't think attack speed by itself is going to do the damage you need. Attack speed is great but without damage it wont do much.
For instance Master Yi's Wuju Style scales with Bonus AD therefor Lethal Tempo does not increase Wuju Style all that much and it seems that Conqueror probably does better job than Tempo
So my suggestion is to turn Lethal Tempo into Bloodrazor based keystone. This is going to indirectly buff the jungle item bloodrazor or champions who use Blade of the Ruined King as well or any champions that rely to onhit effects.
