It seems that nowadays (since the end of last year?) the judge has a "base time" around 0.012 (12ms) - 0.016 if unlucky, 0.008 if lucky, and today, for the first time i saw a 0.004). This effect decreases the competitiveness in multiple way. Newer submissions with same time score were always given lower ranking, but now its even impossible to reach the best time scores (which were run with a base time of 0.000), especially on those problems where the final time is close to zero. Also the variation in the "base time" prevents finetuning/optimalization, instead it may lead to resubmit/spam.
I'm not sure what causes this "base time" problem, but if it cannot be removed than something must be done to "balance" its effect. Re-judging all old submissions (below 0.020ms) is out of question, but adjusting newer submissions (from a certain date/time) with a constant 8ms (or 12ms) is probably possible.