At present in ArcGIS Online areas that cross the 180 degree prime meridian appear bisected even though the data is recorded in Mercator.
Therefore, in ArcGIS Online, provide the user with a Central Meridian parameter so the map can center in the region of interest.
In Desktop the Central Meridian parameter obviates the artificial meridonal break line bisecting the Pacific Ocean region.
This might allow a more complete map Story Map as well.