This is the only champion in LoL that cannot function neither as a tank nor as an AP mage.
I don't care what the stupid stat of his presence and win rate is in garbage ELO (below silver) but he is completely useless.
What I suggest?
Well, either make his E reduce a % of damage or remove that passive and hit his AP ratios over the rooftop. For example:
Q damage = 60/100/140/180/220 (+90% AP)
W damage = 20 + 1/2/3/4/5% (+2% AP) percentage of max HP
E damage = 30/50/70/90/110 (+100% AP)
R damage = 200/350/500 (+100% AP). The range is too small, that's why it deserves a big damage number.