I heard a in a patch review video that a olafs one of the developers favorite champs, so I can't imagine he's ever gonna get nerfed
Have you never heard the term "Olafed?"
Olaf was one of the most heavily nerffed champions between the season 2 and 3 transition.
Riot has proven they're not opposed to gutting Olaf's kit with nerfs.
Even with horrible gear this guys damage is insane, true damage at that...
He's Tanky DPS, that's a common treand with all fighter/tanks.
For the 4 main damage rolls in mage, marksman, assassin, and fighter - they can only realistically build in 1 direction, and they all need a defensive mechanic to survive long enough to do their job.
Mages get range and CC to deal damage.
Marksman get range and mobility to deal damage.
Assassins get a ton of mobility to deal damage.
Fighters have defense to deal damage or a bunch of free damage so they build defense.
So - while Olaf's damage is pretty cray-cray without actually building the same damage items you'd need on other champions, his defense isn't actually any better than that of a typical mage, marksman, or assassin - but he's stuck with melee range, lacking mobility, and weak CC.
If Olaf doesn't build defense he's often stuck in the same bind as a mage, marksman, or assassin that doesn't build offense.