But people who are complaining about coil are complaining about "do this right or instant death" too? If they lowered standards to that level, how is any of the mechanics you mentioned (which one of them already exists twice in FCOB) going to matter where any mistake you made doesn't lead to death AND the healers in the game are already capable of healing for more than half of your health in one shot on non tanks?
People keep suggesting pure randomness but also suggest removing instant kill and adding intervals between mechanics or the speed of the mechanic, which at the same time is neutralizing randomness too. They all sound like half assed suggestions, especially if it comes from people who has never actually experienced any of the fights they are complaining about and are actually wrong about the things they are claiming. Scob in its current form is very mistake friendly and even in it's pre-nerf state, fights like t6 and t7 can be cleared even if you made a mistake on some mechanics. I remember clearing t6 pre nerf with the boss having 4 stacks (that's at least 3 people screwing up and getting eaten by the boss and buffing him up...oh look that's not instant wipe). I remember clearing t7 pre nerf with people dying left and right from petrification. I have cleared t10 with my party where I screwed up and died as I grabbed the boss's attention and the other tank just took massive damage (this should have been chaos and pretty much a wipe but my party reacted well). I have cleared t11 with some dps constantly stepping into the boss aoes and getting debuffs, people splitting up the wrong way and getting half the party killed in the middle of the last phase and still somehow won. My t13 clear had me dying to the boss biggest attacks early in the last phase because I mistimed my defense cooldowns and the party endured through.
People telling you that the coil fights are all mechanics and you can finish it by just memorizing are simply liars who can't make the cut. The fights in their prime has mechanics AND personal class checks. Fight them early and it can be very harsh (a tank can still die if he mitigates a boss attack just on his own and still needs healer's mitigation help). Just because you know something is coming doesn't always mean you have the actions ready to react to it. All of that is removed with gear past the content and echo. Players can be a supbar dps and get through the small dps checks through out a fight with their overgeared gear and echo, they can be a clumsy tank and live through attacks and healers will have less trouble healing through big attacks with gear and echo.