Having done M5S and some of M6S, and also my own opinions of just encounter design, this has to be the worst raid tier the devs have made since Gordias, for very similar reasons to why Gordias was a garbage raid tier. Why?
  • The fights are tested at 0 ping.
  • There is a pretty stiff gear check.
  • The fights are so badly designed and balanced within the implementation of job balance, that certain classes cannot do the fights.
  • The fight design is further homogenizing the game (distinct from HW.)

To expound on this:

The first point, tested at 0 ping. M5S is a ridiculously inconsistent fight. I know, with certainty, mechanics are designed and intended to go off together and in time with the music. I see massive amounts of variance on mechanics. Sometimes I see things like the donut + funky floor fire off together, other times they're desynced.

I am on a 70-110 ping, very inconsistent, makes it extremely easy to tell when things are going wrong, and this is kind of my expectation on fight design as it gets faster. The mechanics desync more and more, they get harder and harder.

Where this becomes damning is I have a friend in Australia, who has cleared at both sub-10ms ping and closer to 200ms. They say the fight is insanely fun at 10ms or less ping. But at 200, it's a hair pullingly frustrating fight. This lines up with my experience. For those who were around for Gordias, its analogue would be A3S. For 3, the laser into autodeath dot based on server tic where healers lacked the time to react to the fight.

Solution: The devs can't make fast, reactionary mechanics. They need to be slow, and they need to be tested on real ping in real world conditions before releasing. There's a reason stormblood has the best fight design. Part of it is the fights are a lot slower.

The second point, Gear Check. While the fight is most certainly doable with competent players, anyone who steps into PF knows that competency is a bonus, not the expectation. Adds phase is a very, very stiff gear check for people who aren't actually particularly good at the game. Where have I seen a gear check like this before? Oh yes, gordias, where the fight took 3 weeks to clear. Obviously nowhere near as bad, it's still very much a "The devs vastly overestimate the average competency of the playerbase."

Solution: Have people of all skill levels test your fights. A lot of problems in fight design become a lot more obvious when you use people who aren't that great at the game. Including things like the dungeons being a nightmare of very much casual-unfriendly design.

Which leads into my next point: terrible class-job design and balance. Anyone who so much as glances at sites like fflogs can see stark problems in job balance. For example, bringing a summoner makes M6S orders of magnitude harder. But it's more than just this. Machinist is also awful. Honestly, most rphys are awful on this fight, if not period, right now. But if you bring a viper, significantly harder DPS checks become a lot easier, because viper fits the encounter design and dps check a lot better than summoner does. To the point where people are bringing double-viper+BLM at times.

But it's more than just this. A fight like M5S means the best iteration of BLM that has ever been made, Stormblood Black Mage, literally cannot exist. The fight is too fast, there's too much movement. Fight design like M5S kills good caster design. It also kills healer and tank design, but that's a problem that we can trace back to ARR and is more a 'This has been a recurring problem since the game has launched, solidified in stormblood,' instead of modern design where it's stale and boring. And, lo and behold, we have an analogue from Gordias. Anyone remember when Paladins weren't brought because blocks couldn't block magic damage, so every fight was DRK+WAR? How AST wasn't brought because, well, it wasn't so much fight design as class design in AST's case, but the point still stands.

Good fight design doesn't constrain class design. M5S has literally killed off good caster design completely. Though this is a problem we have been moving towards since tier 2 Shadowbringers. It's not exactly a new problem, just boiling frog syndrome for people who don't notice it.

Which leads to the final point: Homogenization. When you design fights like M5S, it's further homogenizing the game. Classes like BLM lose cast bars because of fights like M5S. But it's more than this. All cast bars are at risk. When even SMN becomes the most frustrating class to optimize in a fight like M5S because of having a mere THREE casts of 2.8, 2.8, and 3.0 per minute, it hearkens to a much, much bigger problem.

Fight design like tier 2 dawntrail forces a very strict class design. You can't have too many positionals (though personally I hate positionals anyways,) you can't have long cast bars. All healers need to be the same overpowered boring drivel they have been since SB found the hardest possible healer check (charybdis into AOE.) Tanks end up still tanking the same boring way (Guess I press 2-5 oGCDs and stop caring, I passed my binary check!) but this time with 2m bursts happening during these checks, so good luck DRK and GNB. Shoulda played a different tank! I am expecting classes like MCH/DNC/BRD to be further reworked because of the huge disparity on fights like M6S, and that just means more homogenization.

This raid tier is literally the worst raid tier this game has created since Gordias. It has restrictive class selection, gear checks, and fight design that doesn't understand the game's own infrastructure. It is hair pullingly frustrating for the dumbest possible reasons, and further proves that hard encounter design is worse for the game than easier encounter design.

I wish I was on a ping of 5 so I could experience how M5S was intended to be played, because it sounds a lot better than the hot garbage I get to play with.