I've been noticing a trend in the daily/weekly/monthly top rankings. It seems that the more votes a submission receives, the lower the score gets, e.g.:

#3. Saint - Chapter 2 (4.27/5.00, 479 votes and 3,270 views)
now is: 4.10/5.00, 982 votes and 11,281 views

...which would drop it to weekly #6

#8. Who Goes There? Part 5 (4.00/5.00, 341 votes and 1,922 views)
now is: 3.95/5.00, 579 votes and 7,076 views

....which would drop it out of the weekly top 10 entirely...

This behaviour is pretty consistent - I haven't found a submission that doesn't follow this trend.

Maybe there needs to be some kind of additional weighting based on the number of votes, e.g. less than 500 votes, reduce score by 0.1
less than 1000 votes, reduce score by 0.05, etc

Anyway, I am sure with a bit of analysis of the content you would be able to figure out some algorithms to match.

If not, then the best bet for submitting entries is to add them at 11pm on the last day of the month!