Yes, I am prone to over-reaction & shooting from the hip. I should be American! I constantly do my very best to offset it.
I'm interested that your traffic mostly comes from Bing. Microsoft has always given the least traffic of all the major SEs for me, and I could never work out why.
Most of my response was to your declaration of a `12 pages/sec' index being OK, and even apparently belittling the idea that to crawl at that rate may be abusive. I therefore thought that I should add a little more substantia to my claims, and at the same time highlight an on-coming issue that I've seen little commented-upon elsewhere.
Do you think `nebulous' when checking your site load? Or reading the time from your watch? It's not the word that I would apply to an auto-calculated hit-rate. And I do appreciate that you are suggesting other measures are also needed. The problem is that much of what you ask for is on the pages previously linked via their IPs.
The issue here is that there needs to be some method of ID-ing an abusive scraper. Hit-rate is the simplest & easiest, and also accurate. Once identified as abusive, that IP no longer gets any site pages. Only a 403 (or 503), with a short explanation.