Mythical Stormreaver axe has a very low base damage of 223-265 lightning damage. Compared to other axes this is very low. It is also clearly meant for Savagery or Cadence and it needs that damage there. It has bonus DoT but that is useless for autoattacker builds. Nonmythical Stormreaver has higher base damage!
With that DoT bonus it would make more sense for bonuses to cooldown Blade Arc.
Pretty sure Stormreaver has always been meant for Electrocute with Storm Totems and Savagery filler (back in the day it was taken for Tenacity of the Boar/Might of the Bear), for example jajaja’s original Warder which the Mythical was built on or mad_lee’s take on it.
Compare the damage on it to other similar weapons:
Lightning Cadence support got added after the Mythical released when attempts to change Discord to Physical->Lightning were rejected by the community, so to keep it alive in some way, the support was moved to a handful of items instead like the axe and Exonerator.