The only aspect of mining anyone should care about is how many actual coins miners possess and need to sell. I don't think anyone should be trading based on analysing mining.
Mining was designed to take care of itself. No one else needs to care about it. If the current crop of miners can't hack it they'll leave until some others come along who can hack it. No one knows their costs, whether they're hedged, who's buying their coins or what their plans are. It doesn't matter.
You're mostly correct here, but I think there's one thing worth considering.
Miners are investors. When we see considerable increases in hash rate from new equipment coming online, we should assume that miners are bullish and are not looking to sell anymore than necessary to cover costs. When we see the opposite (downtrending hash rate), we should probably assume that miners are bearish and generally selling inventory rather than holding. This is for the same reason that farmers and metal miners sell futures contracts: to lock in a price before it falls.