Ok, It seems to me the 3rd hitter in an order has the best power (used to 4 but it seems to have changed). Bonds, Sosa, McGwire, Cabrera, etc. Also, you want your next best guys 4th and 5th. Its not really to protect the 3rd hitter but to increase runs. If your 1 and 2 are your OBP guys you want your power hitters hitting with guys on base.
Bonds is an exception not the rule though. He changes the arguement because of his gaudy OBP (he walked a lot). This could potential be skewd though because he had guys on base (Aurila batting second with a .369 OBP) in front of him and his HR would have lead to more actual runs. Normally you would want you best OBP guys higher but the type of walks change things.
I don't know why you think the fifth best hitter goes in the 3 hole. Can someone explain this. I just can't see why there is so much importance on the 4 hitter. That spots seems to have slipped in recognition over the years. Also, order of importance seems arbitrary. Is it more important to get on base or hit a guy on base in. You need them both to get the run. Also, some would argue your 8 is more important than you 7. They might be pitched around to get to the pitcher in a run scoring situation or you need them to hit to get your pitcher up so you don't start the next inning with an out.