Xadir:
Im going to be honest. I'll need to check my class ideas to ensure it doesn't exist, given how many classes do exist just in dnd and pathfinder. And don't forget the homebrew.
I will say:
1. Just do your best.
2. It seems to me that one sure way would be to tie the new class to the canon world somehow//as much as possible.
3. Look, as my examples tried to suggest: if it's some kind of thief, knight, mage, cleric, whatever--
some resonance with a fantasy class someone's already thought of is surely going to be almost impossible. Just don't make it
exactly like something found somewhere else. Do your best to put
some sort of unique spin on it.