The Week of the Conqueror buff seems to be bugged. I just did a mission for Ordo Xenos - the mission briefing showed 8 base reputation to be gained, I added Tarot cards, which boosted it to 12 reputation. I was at 251 reputation before launching the mission.

When I completed it, I was indeed at 263 reputation. With the weekly buff it should have been double (24 reputation), no? Is it perhaps the use of the Tarot cards that deactivate the weekly buff?

Edit: actually, never mind, it looks like the buff is applied to the base reputation gain the moment the mission briefing is opened...