@Neo Is Delight
I know you want to keep the idea of Dragon Slayers fairly rare, but since the guild is known mostly because of it's higher than average number of Dragon Slayers wouldn't it in some way make sense that a sort of clique would form from them? And since we'd be focusing on a specific group of the characters rather than the entire guild is it that important a distinction to be made? Surely as we wrote through the RP the number of non-dragon slayers would be made apparent from us writing them as NPC's?
There's a saying I like;
If everyone's special, then no one is special.
If you joined a DC RP and everyone wanted to be a Superman Clone because it has arcs about Superman turning evil and being a god. Then the 1 Superman Clone, no longer becomes relevant because everyone is a Superman Clone. While yes! Generally you would want more Dragon Slayers.
But that doesn't tell a good story. Also it begins to create this power creep, if everyone is a Dragon Slayer and their magic is supposed to be super powerful awesome. Then any ordinary character or villain doesn't stand a chance against 6 Dragon Slayers.
Your two GMs, me and Neo, both wrote normal mages. Yes, I made my own magic and Neo did as well. But! We don't have have Dragon Slayers. I am comfortable with at least 2 or 3 PC Dragon Slayers. But not the whole damn cast. Then it makes my normal mage or anyone else's normal mage irrelevant. And it becomes focused on just the the Dragon Slayers.
Then the normal mages are like "why am I even here"