What did Taliyah do to merit her those huge nerfs?

I understand that Taliyah is a top pick in pro play right now, but is adding 20 extra mana on the spell that she maxes first and uses the most the best way to go about it? Why did they not just revert some of the earlier changes to her Q like the lower cooldown or bonus damage? I'm only saying this because this is going to hit her like a truck just as she is fitting into the meta again, and it's not like she's the best solo Q mid laner at this time.

Plus, quite a number of other mages have gotten buffed in the last patch, and Riot is just going to stick this onto her without seeing how/if the meta changes? Okay then... I also find it quite odd that of the three top mid laners getting nerfs (Taliyah, Syndra, Orianna), hers are the most significant.... yet she is the least oppressive of the three.