I think this is an extremely good analysis where you actually checked numbers to support your claim. I think the tactic of following for people to follow you back is a very poor strategy. It will work in the way that the amount of people following you back will increase, but what does that matter if they don't know you and you don't know them! If you follow more than a thousand people I would claim that it becomes almost impossible to establish any real correspondence. I think one good solid comment is worth a lot more than 10 upvotes!