I don´t like DS much - yeah, I stated that elsewhere, but then again, I will be fair here.

Ever wondered how the Keeper´s compound would look like? (aside from the visits between the missions) And how it would be to go stealthy inside?

Here you go. In the story we are at a point where there is enmity between Garrett and the Keepers. So - we have to be careful. What might be behind all that? And it also adds a plottwist.

Aside that, looting the compound and dealing with his former teachers/brothers(or whatever) is also enjoyable.
And you can even alter the outcome of the council.

The soundtrack is also good.

If more DS missions would be of that quality, I would view it as a better game. Unfortunately, this isn´t the case.

Mission is quite good. But from what I really hated is that in this mission Garrett was allowed to murder dozens of his former colleagues. He wants to find the truth and perhaps redeem himself - but he is allowed to murder every single person inside. Storywise it's just stupid.

Well, then the issue is you can basically murder everyone in the game. Depending on the difficulty. The murder system is nonsense anyway. You murder the member of one of the factions, it lowers the status a bit, but then you can raise it again via the quests.