I feel mages shouldn't have the AP bonus vs structures
Every class has their strength. Mages obliterate teams. AD's provide consistent damage output. Assassins have high burst. Tanks absorb damage.
But did you notice? Mages kill turrets faster than the consistent damage output class.
doing 400 magic damage on hit every second to a turret really just shouldnt exist.
Ziggs passive/Lich bane i feel is fine, just not the passive 50% of ap is applied as magic damage.
You're a mage, not a sieger. You shouldnt be destroying turrets so fast.