Unfortunately the tweet doesn't go into detail about what has actually changed, so I'll give you a summary:
Inquisitors staff piece:
- Extremely rare chance while training within the fort when the pylon is active
- Rare chance while training within the praetorium, where chance increases relative to the level of the hotspot you're excavating
- Praetorium chance is increased if the pylon is active
- Note: The base drop chance of receiving a staff piece from the praetorium has been decreased from what it was prior to the hotfix
Spear of Annihilation tip:
- The drop chance has been decreased