Currently I am leveling to 4* 4.70, so I can unlock 4*+1
Cleric Rigard
Ranger Tiburtus
Sorcerer Sabina
Wizard Proteus
( see Notes for explanation)
All Defense/ HP grids
And if I had Cyprian I would add him to the end of the list as all attack grid Paladin Cyprian. But all defense grid Paladin Guardian Falcon would go first for emblems if I ever get either hero.
And if I ever get through all the above 4* purples- Sorcerer Cheshire Cat is rumored to be a 4* purple so Cat would be after Sabina for emblems but I would immediately take him to 4* 3.60 because OMG
So the above is my personal recommendation of purple hero order.