To put things in perspective, Zoe is a nightmare in balance.
Now, I'm not the one to say something is OP and what isn't OP, I'm just pointing out facts here. I'm just going to compare 2 champions that both go mid lane that have a "similar ability".
Zoe's W: Has the potential of hitting a champion 3 times via 3 bolts.
Ahri's W: Has the potential of hitting a champion 3 times via 3 bolts.
Seems fair, right? Except...
PASSIVE - SPELL THIEF: Whenever enemy champions cast a Spells icon summoner spell or item active, they drop the corresponding Spell Shard onto the ground that grants Sight icon sight over a 100-radius area and remains for 40 seconds. Some enemy Minions Killed icon minions spawn with random Spell Shards that only drop to the ground for 20 seconds if killed by Zoe.
Collecting a Spell Shard allows Zoe to activate Spell Thief within the next 60 seconds. She can replace her current Spell Thief active by moving directly onto another Spell Shard.
ACTIVE: Zoe mimics the active of the collected Spell Shard.
PASSIVE - WHEEEEE: Casting Spell Thief or one of her own summoner spells grants Zoe Movement speed icon bonus movement speed for the next few seconds, and summons three bubbles that orbit her for the next 10 seconds. The bubbles autonomously hurl themselves at the nearest enemy in range, prioritizing her attack target, dealing magic damage.
75 / 105 / 135 / 165 / 195 (+ 55% AP)
Zoe gets TWO passives and an active in the same ability, ON TOP of doing more damage alone, gets 30-70% bonus movement speed for 2-3 seconds (Scaling by level), takes summoner spells that you use, and uses them against you, as well as items, and is an RNG mess in lane.
What does Ahri's W do in comparison you may ask?
ACTIVE: Ahri summons three spectral flames which orbit her for up to 5 seconds.
Flames prioritize champions hit by Charm Charm or any enemy hit by Ahri's last basic attack, within 3 seconds and Range icon 725 range.
After 0.25 seconds, each flame targets a prioritized enemy, or after 0.4 seconds pursues the closest visible enemy in range, prioritizing champions, then the target of Ahri's last basic attack, dealing magic damage.
MAGIC DAMAGE: 40 / 65 / 90 / 115 / 140 (+ 30% AP) Multiple flames can hit the same target, with each flame beyond the first dealing 30% damage.
Ok, so not only does Zoe's W do more damage, but Ahri's W does less damage if more than one gets proccd on an enemy champion. They're basically the same ability in concept, yet Zoe's got like 7 other things going for her.
This is why people are bitching about her, of course I know there's other problems like how she can nuke you from 5 screens away, has true damage, has no real cooldowns/mana costs and has a sheen in her passive, but this was just an example.
Still is