My logs are showing historical % only as "-"
Log
You can see “-” from yesterdays log (Tue April 19 2016) on 1st 6 bosses.
Google it, waited for a day… There was a weekly reset, in a case you are updating once a week,
but still its just a “-” 
Those pages don’t attempt to estimate ranks above the cutoff. I should probably fix that to give you an estimated %. I can’t give the precise rank past the cutoff though since the page would take forever to load if I did.
I’m afraid i do not follow… I understand some general technical things, but what is a cutoff and will I have this problem later?
Ranks below 200 are not shown on that page, as crawling the ranks to find your exact position would take too long for all bosses. If you view individual bosses, I increase that cutoff to 5000, so it’s more able to give you results.
It’s on my list of things to improve to estimate your rank like I do on report rankings pages. I just haven’t gotten around to it yet.