So i was watching a streamer go thru this fight recently(in the last 2 weeks). Everything i wrote above is still 100% true. The script has not changed, the stat squish does not matter. But the streamer i was watching was struggling with the fight. Why? For starters, they were trying to kite the boss around the room. Dont do this, it is very dumb. The boss can still hurt you, but you cant hit it back. Then they would go into a tunnel vision on just the boss and aoe markers, leaving the extra mobs to not only repeatedly attack them but drop more aoes on the ground forcing the streamer to keep moving more then they needed to(which lead to less damage, then them trying to kite again when health got low). Then they finally got to the circle of magitech bits. They started by ignoring the adds, then they went around and tried to kill them one by one. Neither of these works, as there are too many to kill individually and after they fire off a few lasers they all go into self-destruct mode at the same time and end you. The next pull, they got it. And while the streamer was getting advice from chat after each try, it was only advice on what they had already seen and failed at - no hint at mechs to come(specifically i was watching this part on VoD, as they did the fight before i got off work and couldnt help live). In the end i think they went 5 pulls to a clear. You can clear on your VERY next attempt. Here is my updated and slightly simplified strategy.
Press 1. You can ignore 2, you can ignore 4. Press 1. Every chance you get, press 1. If you arent comfortable enough playing to pay attention to mobs spawning, then just focus on the boss and pressing 1. The first time you will want to use 3 is when the circle aoe's start appearing on the floor(in the above guide, this coincides with the troops on the bridge becoming targettable after giving the weapon an updated move set). Using 3 once will make them stop for awhile, then go back to 1. Around here a pair of airships will appear to attack. You can kill them both with 2 or 3 uses of 3, or quick swap targets and 1 them down. Again, if the circle aoes restart hit a 3. Then when the star-burst pattern aoe appears, 3 again. And your final 3 should be when the room fills with explosions. Any time you arent hitting 3, try to hit 1. Finally the script will fill your LB(5), and you end the fight in style. The fight is a tiny bit faster if you can mix in some 2 and 4 uses with your 1's. But all it really takes to get to the end of the script is: avoiding some of the aoes, consistent 1 usage(this will keep you at or near full health), and being reasonably quick eliminating the extra threats with your 3's.
So there you go, the 3 button plan. And the fight will still be over in like 4 mins.