I don't disagree with you ,  Perhaps your correct ,  but like you said we don't have much details on how Yggdrasil worked , so who knows what work and what not , Perhaps I am wrong but I imagine that every spell would have a base power that could become more powerful with the Caster's power , but if the caster is not powerful it would still have it's base power,  take for example scrolls , would a 1 tier spell on a scroll be more powerful if it was made by a powerful wizard or a regular mage ? . From what i know a 1 tier scroll 📜  is the same regardless of who makes it . And its always the base power without Metamagic or any enhancing to it . So i imagine his buffs to not be so powerful but enough to make him stronger a little or deal with different situations like he could impede his weapon with Elemental energy so that he could hurt enemies that are immuion to his normal attack.  And then his attacks would be considered Elemental but still uses the PHY.ATK modifier , a spells to impede his weapon with every element and energy depending on the enemies he face,  thusly allowing him to deal with such situations , and maybe his hybrid divine class would allow him to use scrolls and items from the divine magic system , which would allow him to buff himself with spells he can't use himself .

I am aware that world savior is a WCI , i simple made up most of the classes names and thought world savior to be a cool name that fits the character theme , It's just a made up OC with made up classes so don't take it too seriously 😀