His e is balanced BECAUSE it is overloaded. His e is basically his entire kit. Every other ability is weak.
Passiv: ignores unit collision + a little bit less damage from AAs <== a generic "we need a nice to have, but nothing powerful" passiv.
Q: low range, low damage, single target, not reliable. Basically every comparable ability (irelia: longer range, reset on kill; diana: longer range, higher damage, reset on q; yasou: no cost or cooldown) is stronger. Only two things make this ability at least not useless, the on-hit proc and the fixed distance.
W: just a AA modifier, again basically every comparable ability is stronger (kayle: range, damage, aoe; kassadin: mana sustain; ekko: shield, aoe slow, vision and stun). Again only the %missing hp dot prevents this ability from being completely outclassed.
So we have now 3 abilitys, but still no: cc, waveclear, burst, escape, poke, longer range engage or good defense ability.
And because his e has everything except poke let's add high earygame cooldown and super high mana costs.
You can't save your e as disengage or dodge if your want to burst somebody down, you can't waveclear if you are low. It would be a huge buff for fizz, if they would shift the cc, waveclear, burst and long range engage component to his other basic abilities