Reprobate
I would've preferred if Hitogami has directed Rudeus to get Magic-Eye from Krishika so that his Magical-Skills can improve & due to this Rudeus should've mastered chantless incantation for Heal, Detox, Divine & Barrier Magic as well as learnt to control ambient Mana to boost his spells. Eventually with Julian's help, Rudues should've mastered at least Heal & Detox Magic upto Emperor Rank but with time, he should've improved himself to God-Rank in Heal & Detox. Thus Julian should've requested Rudeus to Ressurect Luke with God-Rank Heal-Magic.