The other major problem stems from the fact that although most of these characters (if not all) will play the role of companions during the game, even though they weren't written as such. If I'll write harry potter's character as is but tell the whole story from Ron's point of view, I'm doing something wrong.
This right here. Right now I feel like the MC 'is' the side-kick, as least as a custom character. Don't get me wrong, I like my party members to have history in the world and quests, etc. What I don't want, personal opinion, is for them to be the main character that my customer character is tagging along with. If someone you pick up along the way made some bad bets in his past and you run in to his bookie and suddenly you're trying to sort out that problem, fine. I don't need my companion to be a literal bomb that TPKs me when I get stuck in a post battle conversation with his spectral image. Not sure where they are going with that but it feels like the kind of one in a million 'Main Character' type of situation.
I think I'd be happier with the story if you were the only one with a tadpole. Give the MC something special.