The indirect buff that pushed Sion over the top.

As most people are aware right now Is well OP. He is the most picked top laner, the highest win% top laner and quickly becoming one of the most Banned top laners. So why did he become like this without major buffs to his itemization or his kit? Some people think Runes reforged specifically comet for the poke in lane, while the new rune system certainly is nice for Sion it's been out for quite some time now, IMO we would've seen this quicker and Sion is also preforming well with Glacial augment and other rune choices. Which leads me to believe it's something else.

My explanation can be found in 8.2

Targeted damaging spells draw minion aggro.

Champions with spammable targeted spells, like Pantheon and Cassiopeia, put opposing laners in an awkward position: fight back and draw minion aggro, or just take the punishment they hand out. Changing this mechanic will make those champions a lot more intuitive to play against, as well as easier to balance. 

Why is this really good for Sion you ask? Well due to the long range of his E he effectively is one of the few champs in top that can still spam poke during lane phase, making Sion a lane bully along with being a Strong Tank.

Here's to hoping his CD/Mana cost or Damage of his E is nerfed in 8.5