The maintenance is complete, and the PTS is now back online and patch 10.0.4 is available.
Maintenance for the week of May 13:
• [COMPLETE] ESO Store and Account System for maintenance – May 14, 9:00AM EDT (13:00 UTC) - 12:00PM EDT (16:00 UTC)
Sergeant Mail - Heavy Attack
Latest PTS patch 6.0.4.
After some testing.. the Sergeant Mail set no longer applies to Power Overload heavy attacks.
On ESO live, and patches 6.0.x-6.0.3 Sergeant applied to Power Overload heavy attacks. There is no mention of the change in any PTS patch notes. So I can only assume this is a bug.