Why is Olaf getting buffs on the PBE if he's statistically one of the best top laners?

For reference, here is his op.gg http://na.op.gg/champion/olaf/statistics/top

He's getting : +0.5 AD per level +10% AS while Vicious Strikes is active E CD reduced by 4/3/2/1/0 seconds.

As far as I know, you don't need much to make a champion broken (as an example, Morgana's winrate jumping to 60% even though her lane sustain was heavily reduced).

I think it's safe to say Olaf will be nerfed or hotfixed shortly after, why not buff champions that deserve it instead of champions that are already doing fine?