Well… We all shouldn’t always think within the frames of things.
Like chivalry doesn’t always make a person a holy paladin (It can be roleplayed as anger or battle experience or whatever) magery doesn’t always have to make a person a mage as long as it has limitations.
Now of course a monk shouldn’t go around summoning earth elementals etc but maybe they should limit themselves to only healing spells and maybe fire spells?
The fire spells could represent them waving their torches about and setting someone on fire?
And the healing spells would simply be good healing preformed by the monks.
But that’s my two cents on the idea.
As for Arc... I don't consider him a necromancer just a very talented mage who's learned more spells then less experienced mages.