Ryze is not picking up his mana scaling
with 1250 bonus mana his q only does +30 magic damage and that means he only gets a (120)+30 shield when he gets run down. many tanks can all in ryze since his mana shield is down right now.
now if he was at 400 ap he would have a 400 damage sheild. now that seems crazy but i think the mana scaling on ryze is down right now.