As per the title: The non-construct-combo (normal) version of Minigun is not stacking the hit counter. This applies everywhere that I have tested. PvP & PvE. The damage, pushback and other effects appear to be functioning normally, only the damage to the target is not increasing the hit counter. Additionally, the AM or Construct-Combo version of Minigun appears to be unaffected by this bug and stacks the hit counter normally. Here is a video I recorded displaying the bug:
After noticing that the 'bug' extends to all of the normal versions of the HL abilities I contacted a friend who said that Might-based abilities don't proc the hit counter. If this is the case, then things are working as intended and I made an error posting this as a bug. That said, it does seem counterintuitive to have two identical abilities function differently like that. Although now I guess I know why people choose fan.