Do not buff Ryze yet
It's undeniable that the win rate is very low, but it's only been a patch. I remember Ryze being buffed in patch 5.10, then being hit by torrent of nerfs until he was in the spot he was. I plead to leave Ryze unchanged for a few patches, before observing how he does in various levels of play.
Never had more than 4 upvotes before. Keep practicing, and you will master the Rune Mage!
Edit a month later: My win rate for past 20 Ryze games is 65%. Much better than pre-VGU Ryze. Edit 8 months later: He got nerfs even! Well I'm down to 58%. Keep trying.
and then after that is a half way stacked 