Why mages have taken over top:
Spectre's cowl nerfed hard. 15 health regen to 100% (when most champions sit at around 8-10 health regen) and 10 magic resist removed. OH BUT HEY, IT LOST 200 GOLD HURHUR.
BV nerfed hard. 45 health regen to 100%? Most champions struggle just to get 33% of that.
Hexdrinker price increased by 100.
Spirit visage nerfed hard. 20 health regen to 100%? Spectre's cowl went from 15 to 100%, and SV goes from 20 to 100%? What is this?
Level 6 health reduced, mages can autogib on their ult most melee now.
Mages are more survivable (hourglass) more damaging (dur) are better at initiation (hourglass) give better gank assist (due to better laning phases, and generally more/easier CC) and as just mentioned, lane better! OH also they have 50% healing debuff for free