If you nerf Sion's E then give him more mana regen accordingly.

On the PBE Sion's E goes down from 50% to 30%. Sion has a strong lane push but weak dueling potential. This translates into a massive nerf, since this will effectively reduce his pushing pottential which leaves Sion with very little to desire when faced with a 1 v 1 scenario.

I explain: When doing 1v1 top lane, sion has to harass with his E, this move is easily dodged except if it is used vs minions to push the lane. the problem is that Sion struggles with his mana regen which balances him out because if you pop your E ,Q, W combo you will be left with low mana to fight another round. This balances Sion well because he can only trade hits when he has mana available but if you have a nerf to his E, the mana issue is accentuated exponentially so I hope that they will acompany the nerf with a boost to his regen otherwise im afraid you will not see another Sion in a long time.