imo, what caused this issu is the slow nerf on his q, now it is nearly useless unless you have teammate nearby. (Now you are always kitted and rarely can anything about it).
Olaf kit his very unique, i dont know any viable champ that fit in the role he had (kill the enemy carry no matter what), while still being tanky and laught at the enemy cc. (i think popy is simular to olaf gamplay wise, but she isn't in a good place too...)
tell me if you find someone that can do what olaf does while still being very viable and I'll will be very happy.