I'm not sure I understand what you're saying. The IFF timer has nothing to do with the how many DLC missions you have, It only depends on when You do the the reaper mission itself; if I'm not mistaken, a day 1 player and a owner of all DLC could have the same problem or no problem at all; furthermore, I tried Overlord and I'm pretty sure It counts as One total mission, not as the 4 it really seems to be: I remember doing this right after the IFF mission and after Overlord I still had time to do Legion loyalty.. What changes with the DLC is Horizon; I heard that some people reported Horizon triggering before all 5 squadmates were taken (Never happened to me)