I think it is best to weaken the armor of Q, 25-35, change it to 15-30, the basic shield of W should still be weakened, but delete the 30% remaining HP cap, which is very reasonable, because Olaf It's not the damage that's missing, it's the toughness.
Right now the internal perception is I don't need further nerfs (big caveat we are still actively testing for balance on him, so that could change quite quickly), but the amount of armor shred on Q is very high on my list of things I'd nerf next if he does need more, for what it's worth.