Mages should go back to what they were in season 3
Unless you were swain or vladimir, you were squishy.... ex: Karthus, veigar.
Mages had a clear role of either late game team fight: Cass, maybe veigar, anivia, and ryze. OR they had assassin burst or early game i.e.: annie, ahri?, and some others like leblanc.
and all other ADCs that build health to be squishy as well. Nerf 
etc. tankiness capability then we can talk about making mages squishy.