just dont put true dame on infinity edge crits.
it should be more like something along the lines of fervor of battle, or an attack speed buff that applies and refreshes on crits. just a more conventional method of increasing dps.
i really dont like this new trend of giving every carry true damage. be it via conqueror or the new infinity edge. conqueror could just grant armor pen. the problem is like you stated, that it kinda shits on % damage reduction abilities in champion kits, that are intended to be good and absorb a bunch of damage when utilized correctly.
i dont know. this just feels like a dangerous path to go down. they might have to compensate by ramping up the % damage reduction values of all the champions who use the stat. which sounds like power creep and a binary relationship. % damage reduction becomes op when you dont have conqueror or infinity edge, or its useless when too many people are running it.
its going down the same route as grievous wounds and heals, where one of the two always seems way too strong.