I attempted this quest a bit ago and felt that it was oddly more trying than usual. I noticed that enemies were level 80 and I was not, which shouldn't be that bad. However the AIS in this mission is scaled to my level and not the level of the mission/enemies. For reference, my AIS laser against the core area does 150kish. As you may see in the video below, the laser does 250k damage from this player in the same quest with the same setting. Bear in mind this damage ratio applied to all attacks. As you might guess, this makes the mission much, much more difficult to complete, not even taking account the defense and hp differences inherent in a lower leveled AIS.
Given this, it is likely not possible to meet the strict requirements for S rank on this quest at this time and any player attempting it will have a far harder time than a normal player on the Japanese server due to the scaling, not to mention lack of access to higher level and crafted PAs.
While we will eventually have access to these things assumedly, a temporary nerf/scale down to the player in this mission, or at least an AIS level scale up, may be a good solution for the moment since the quest is available. As is, it is honestly rather unfair.