There's nothing more difficult in this world than convincing someone of an unfamiliar truth...
I'm very easy to convince if your argument has substance and is based in fact, but so far the only arguments I've seen are merely statements that I am wrong or, even less persuasive, that I am an idiot. Since I've designed entire drive systems for locomotives for my day job I'm unlikely to be convinced I'm an idiot just because some random dude on the internet says so.
Again, I am more than happy to change my testing methodology if a reasonable explanation can be given as to how it could be so flawed it would result in a 30% difference in coins earned on two consecutive days based on reported hashrate and average difficulty on minethecoin.com (not a snapshot of earnings from whattomine.com).
...
Someone took the time to explain what I was missing - that luck varies on a per-share basis, not just on a per-block basis. I still find it hard to believe that luck on a per-share basis could cause one miner to make 30% less than another over a 24 hour period when the pool finds a block every 2-4 minutes, but I can see it is at least possible.
Also, I tried running ccminer-klaust with a fixed difficulty of 512 in preparation for a retest and surprise-surprise, I only made 63% of the expected number of coins based on average difficulty... So that kind of cinched it for me right there.
I'm going to restest the two miners concurrently using the TZC pool on altminer.net as it doesn't require registration, an issue which has prevented me from registering a second payment miner/payment address on the TZC official pool.