What were you expecting to happen, and what actually happened
The Berserker spell Split Skulls is listed as dealing melee damage. The Barbaric Rage effect gained from matching the Rage gems generated by the Berserker Ultimate says the following:
Therefore the damage of Split skulls should be doubled whenever Barbaric Rage is active. However, this is not the case. In the screens below, Barbaric Rage is active and Split Skulls is listed as normal for my current stats as 2,410 as seen below:
When fired, Split Skulls should therefore deal 4,820 damage. As seen, only 2,410 (9,704 less 2,410 equal 7,204) damage was inflicted:
How often does this happen? When did it begin happening?
Always; this has been happening as long as I can recall and was referenced here by another player:
Several other reported items bugs in the same thread have since been addressed (Holy Avenger, Wither, Terror, etc.) but this remains outstanding and is not listed as a known issue. If this is intended behavior, then the text should be clear that Spell-based physical damage is excluded.
Steps to make it happen again