Sadly, things like Level and HP don't translate very well into lore/RP mechanics. They're purely an abstraction and there's little to no mapping between the two.

Like you said, Brass Blades will show as level 5 but serve their purposes in story scenes regardless of any perceived level differences (being vague to avoid spoilers).

Thinking of level in this way is similar to thinking of HP in a case of getting hit by that bad guy's axe twenty bajillion times and still not dying. Sure, you can say that Curative magick is potent... Or you can say that HP is an abstraction of your resolve to not go down, the defensive capabilities of your armour, the assistance of magick and any other numbers of factors that all get nicely wrapped up in that set of numbers.