The Lagonian Shamanism node is supposed to grant gladiator stacks on tempest casts at a 30% rate, which it does normally.
However, tempest casts made via the Druid’s Call node (25% chance to cast tempest on melee while transformed) do not grant stacks.
I second this, it’s kinda holding back my build 
please fix
seems several of the tempest strike nodes aren’t working correctly in form which is a bummer