Just checking with those that have had a chance to compare an existing 480V study with the same study done in 1584/2018. I run Easy Power and I have taken a couple of studies that were run in 1584/2002 and changed the electrode config to either Barrier or Horizontal, everything else was left in the default mode. In all cases the 1584/2018 IE results are 25% to 35% of original findings done with the 1584/2002 version.

Is this what everyone else finding, especially those running SKM and ETAP

I've seen both higher and lower. See the thread on "Low arcing current" for one case comparison.

Yes it is possible, The arc current variation with selection of Conductors VCBB or HCB may yield those differences. The arc current variation is also considered for medium voltage studies which was not considered in the IEEE 1584-2002 standard

Regards
Raghu