I tried again with increased intensity and the reject rate has jumped.
With my usual -I setting i get over 9% rejects. But this way i get over 1770 WU and higher hasrate.
With reduced intensity i get a little over 1400 WU and lower hashret but between 2% and 3% rejects.

Which is better ? The WUs are the actual work units, so the higher number - the better and rejects are considered, correct ?