The thing is, I understand exactly what you are saying as far as I have to have a large mound of data in order to be able to decipher between good and bad days, so that I may be able to decide if this just happens to be a bad day. Things like conversion rate, click through rate, position, etc. - I'm sure all of these things play a huge role in conversion.
But the thing is, I have a presell page. The first half of the day, up until 1pm, I had 150 different "eyes" that made it past my page, and on to the merchant page. So as far as initial click through from my landing page to their merchant page, that's 150.
Later that day, for the last 8 hours, I have 150 more clicks onto the merchant landing page, from my page, and no one converts.
If over the history of my landing pages and ad copy, which I have nearly 3 months of data on, I have an avg eCPC of $.55.
I understand you have good days and bad days, and holidays, weather, tv shows all affect your outcome. But in this case, its same day. The leads are pouring in, then they halt completely? The click through rate didn't change, the number of clicks didn't change, my avg position has never changed, i'm using 2 different PPC sources equally.
With all that said, it is highly unlikely that you would have a good normal conversion rate for the first half of the day, then it would completely go to shit the next.
I've had experience in the past with a different CPA company, where I'd be killing it all day, then in the afternoon, my leads would really start picking up as kids were getting home from school. I'm talking $400 - $500 per hour I'm clearing on leads up until like 9pm, when the tracking would "freeze up". They would say, "oh the leads are still being tracked, even though they aren't showing up in stats." Then the stats would update, and i'd have a shit ton of clicks, and a whole lot less leads.
This happened 4 days in a row, on the 5th day, it happened at night again, i switched my links to a competitor, and the leads POURED in. They were fucking me, and although I had no proof, I knew.
This current situation feels like the same thing.