Mages are the only champions that have to back in late-game when low hp

Adcs can go to a creepwave and just lifesteal to full health Tanks have good regeneration from their items but mages still have to back everytime they get hit (even if its just some poke, like jayce e+q). I don't think mages need that kind of weakness in lategame, considering that they are so much weaker than adcs already (only comparing lategame).

Spellvamp won't work, so I suggest to invent an ap-item that has a passive similar to warmogs, just with a 350 ap requirement or something. (Out of combat: 25% maxhealth will be restored in 5 second. But this passive is disabled if you have less than 350 ap)