Because let's face it, E and Q are basically one ability. They're getting combo'd together every single time E is cast.
Even with the upcoming nerf to his Q, bringing it from 180 base damage to 165 base damage...
#No champion should be able to spam 475+120% AP+8% bonus mana in damage every ~1.35 seconds.
1/4 the CD of most champs' primary damage spell at max CDR (~5 seconds).
Over 1.5x the base damage of some of the highest base damage (~300) skills in the game.
1.7x the AP scaling of some of the highest AP scaling (~70%) among 'spammable' (~8 sec and under) abilities in the game.
And on top of that he gets 8% of his 2600+ bonus mana, which ends up being 200+ damage.
To reiterate, he has the:
Lowest CD skill in the game outside of resets or Cass. 1.35 seconds.
Highest base damage of any non-ult ability. 330 from Q alone.
Highest scaling of almost any ability in the game, barring a select few ultimates. 90% from Q alone.
Additional damage scaling that no other champion in the game has. And he builds a massive amount of that stat without sacrificing AP. 6% from Q alone...
######And for those of you that are going to argue that his E/Q are not one ability, all of these still apply if you subtract his E damage :)
Until his E/Q (and R bonus damage) interactions are completely changed, Ryze will NEVER be balanced.
There's a reason Tahm's R bonus damage was removed from his ult and changed to his passive. And completely removed from his primary damage abilities. Leave it to Riot to re-use a more powerful version of a failed concept without any drawbacks.
#AGAIN, THESE NUMBERS ARE ALL AFTER CONSIDERING THE UPCOMING NERF TO HIS Q.