Patch notes are available for 4.06 which lands a little later this morning.
A simple list of what appear to be quality of life alterations encompass the total of what is being addressed,
- 5 classes/jobs get potency and duration increases while Gauss Barrel from machinist receives a reduction in recast from 10 to 2
- Grade 2 -> Grade 5 carbonized matters receive a huge rebalancing for NPC pricing going from a 50gil -1000gil scale to a 4gil -14gil scale
- Many fixes to the various parts of the game where under the perfect conditions things went wrong have been figured out (apparently) and fixed