I'm also afraid to tell you that 'luck' does not exist - you can calculate probability but not luck (unless someone could post the calculation for the likelihood of luck existing)...
'Luck' exists, silly! If you earned more than expected, you've had good 'luck'. If you earned less than expected, you had bad 'luck'.
One certainty is that as the pool grows then so does the traffic into servers and it doesn't matter how much hashing goes on, it has to get to a server and 800-825TH seems to be the current 'lucky' number range.
No, the traffic problem is what vardiff solves.