I think 300 is really nice. I'm not fully remembering the exact numbers. But Steemit has close to 1,000,000 accounts. And I think less than 150,000 are active. So that's less than 15%. That would mean about 300 active users. Precisely what you would expect.
But I think if you analyze even further you do a bit better. Among your ghost followers are also some bots. Those bots are included in the 150,000 active (if they upvote). But those are not included in your 15% active users.
Good point. So maybe I am doing better than the average Joe in percentage of non deceased followers.