People need to stop comparing world first race shenanigans as balance.
There isnt much problem with raids, apart from the fact that usually the 3-5 bosses of Mythic difficulty are easier than the AOTC boss, or the previous one also.
Sepulcher might have been a bit harder but this was explained that it was two raids merged in one so it felt longer and had 2 "end" bosses in it, so comparing it to the previous raids/years is also wrong.
As someone that does HC only for the last 8 years, what is problematic, is the scaling.
Raid with 10-12 people, Ability X takes everyone to 40%, raid with 15 people, ability X takes everyone to 65%, ability X2 that comes right after might kill someone at 10man raid size, no one ever dies at 15 man raid size cause they were always much higher %.
"Ability targets 3 people and they have to run out", at 10man, thats 30% of the raid and if it targets your highest DPS cause bad luck you start having DPS problems and then at 25 people "LOL WHO GIVES A FUCK, PEW PEW ITS STILL ONLY 3 PEOPLE"
Thats literally the only problem raiding has, how much easier to irrelevant levels HC becomes cause the scaling is off, obviously Normal has this problem also.
Cause the mechanic is made from Mythic and 20man and scaled down "damage" wise but not raid size.