Ok, let's just remove the ability to decimate your opponents if you get fed via playing well.
? Oh well, your infinitely scaling ap is now useless against anyone but the TANKS.
? Sorry, you can't execute anyone(even the VILLAIN) above 10% of their health with your ult, despite the fact that your ult IS A EXECUTE.
? Well, I guess you can just resurrect people, as your ult used to do 100000 true damage to those it resurrected after 10 seconds, but now it just does 10% of their health.
? Oh you got fed? Sorry, but you will have to do your combo 10 TIMES in order to kill the just reconnected lvl 1 adc. BECAUSE FAIRNESS.
Do I need to go on, or did you get the point? (If not I shall up the sassiness in my next response) None of these people are assassins, but they all rely on doing exorbitant amounts of damage in seconds, sometimes not even just 1, and it would screw them, and a lot of others, over. The game would have NO kills, because it would take 10 seconds AT LEAST(20 for anivia) to kill even the weakest, squishiest, most underfed player. AND DID YOU EVEN THINK OF HOW HARD IT WOULD BE TO LAST HIT MINIONS?