I remember that when I played this level the assassination objective was actually one of the positive highlights for me. While Garrett is not necessarily a murderer, in Circle of Strain 2 the killing can be done very stealthily without alerting any guards, so it is not too removed from the original gameplay.
According to the official statement from November, significant progress have been made in the recent months and the campaign is closer to completion, though there is still some remaining work to be done and the team wants to prioritise quality over rushing with the release. They have an undisclosed release schedule, so you can be sure the campaign will be out at some point in future, just be patient.