So when looking at the dat files, there’s an attribute called ‘blast attack level’. As I understand it, the number has to be higher or equal to:
0 - Dmg res
1 - Dmg trees
2 - Dmg Nearby units
3 - Dmg only targeted unit
But the Berserker and Elite Berserker have this set as 6. What does this 6 signify? What makes Berserkers the exception? Edit: it is not an exception, as noted by the post below.
All infantry units have their blast level set to 6. This is because of the Druzhina upgrade. Blast attack levels 4-7 are the same as 0-3, with the added effect that if the unit has a blast radius, it will deal a flat 5 damage to all units within that radius when it attacks.
What Druzhina does is then simply to add a blast radius to all infantry units, so that this trample damage effect takes place.