Evelynn getting Sej'd
For those who don't know, the Sejuani factor refers to a champion who is nerfed specifically due to their interactions with an item, then left unchanged after the offending item is also nerfed or removed.
Evelynn had a mana cost attached to her W, Dark Frenzy, a few patches ago. The Balance team stated this was due to her access to Runeglaive, which, among other things, gave her an additional 250 mana early.
Runeglaive has been removed and is replaced with Runic Echoes. This item will give Evelynn a way to restore mana in the jungle, but it doesn't help at all in ganks and team fights where Eve is supposed to cast W multiple times (that IS why it has reset mechanics, right?)
Without the extra mana pool from Runeglaive, Eve doesn't need higher mana costs to keep her Q spam in check. Revert the W nerf.