Nidhogg EX and Shinryu EX on release were harder to prog than P6S or even P7S. Some tiers have absolute stinker 3rd fights. Actually, more tiers than not have stinker 3rd fights, it's like SE peaked in SB and it's been downhill since. Compare Halicarnassus, Guardian and Omega-Beetle to things like Agdistis, Fatebreaker, or god forbid, the E7S bird tornado. 3rd fights in this game have an annoying design tendency to fall into a trap of 'do comparatively simple things for the first 60% of the fight, and then have all the complexity of the mechanics backloaded as hell', making progging annoying (go through 6 mins of sod all to get back to Deaths Harvest in P7S, only to immediately wipe to it again), and farming boring because you skip parts of said backloaded complexity. Like Fatebreaker, Cycles were interesting in earlier farm, but by the time everyone started getting gear, you'd start skipping some of them
You could argue P11S is in a similar boat of 'it's easier to prog than 'NidEX on release', having only 3 'prog points' of Shadowed Messengers, Dark and Light, Letter of the Law, but P10S is the filter of the tier that you have to get through first
Body checks have existed since like, HW. Nidhogg Fang/Claw phase, Zurvan meteors etc. The difference is that the modern body checks are instant pass-fail checks with no chance to make up for the 'failure', eg by overshielding the heck out of a Zurvan meteor getting missed. Body checks themselves are not the issue, SE's reliance on 'you need 8 people alive going into this or you're instantly die' is
Thanks to the way ilvl sync works, by the end of the expansion it was faster to kill Lak EX than it was to kill the story mode version, because HM synced you to level 69