Since Specters of the rail, Dark Sectors and Trials had halved credit rewards.
In Hotfix Specters of the Rail 2.1 on August 10th, 2016, Dark Sectors were fixed as per:
Fixed Dark Sector Credit rewards being unintentionally cut in half.
It has been months since this update and trials are still reduced. If this is intentional I would like to be informed. This fix would also incentivize people to play raids more, especially after the Secura Lecta change that was made a while back