You know if you are able to do enough damage by doing the Stone, Sky, Sea dummy for M8S. Yes, go right for the M8S test - don't bother with the M5S test. If you can defeat that in the timer, then you should be beyond good for M5S and are clearly able to do your basic rotation well enough that you can contribute the bare minimum in a vacuum. If you fail it with 1% left, don't worry, you can put that down to crit RNG and will probably beat it if you repeat it anyway.

You know if you, as a collective team, are doing enough damage, by if you see enrage or not. Seeing it means every member of the team should try to do more damage. They can achieve this by looking at:
  • Aligning powerful attacks with raid-wide damage buffs better.
  • Using the latest HQ food (Mate Cookie)
  • Using the latest damage potions and aligning them with raid buffs (Grade 3 Gemdraught). Technically you can get up to 3 uses out of these, but often you only manage 2 before a boss dies.
  • Avoiding damage downs.
  • ABC (Always Be Casting). If the DPS check is not tight, it can be alright to focus on mechanics just so that you don't wipe the party and waste their time, but as you get comfortable with the fight, you'll probably find it easier to ABC during difficult mechanics.
  • Crafted gear with full pentamelds (5 materias added, which involves losing lots of materia), and the Ornate body (5 guaranteed materia slots makes it almost as good as max ilvl gear due to crit+dh+det).
  • EX4 weapon.
  • As much Mathematics tomestone gear as you can get (currently 3 is possible, soon a 4th).
  • Party composition - there is the 5% damage bonus for having 1 tank, 1 healer, 1 melee, 1 magic and 1 ranged physical.
Quote Originally Posted by Hastatus View Post
In M5S I have seen parties who I thought sucked because there were DDs and deaths all over the place get less than 1% because somehow one or more are doing insane amounts of damage while other groups who have almost no DDs are barely able to get to 5%.
Pretty good sign that those party members were just not doing the above things that I listed. Probably new or casual players that don't know basic things like ABC, pots and snapshots. Having played this game 10 years I can tell you that beating enrage of the literal first floor in week 1 is only gonna be really hard if the rest of your party aren't good. I mean, in many tiers I've still seen enrage in the first floor up until the 7th week, but that was when the rotations were harder and more punishing, y'know.

I jumped into M5S yesterday again with a party that had just farmed out a full set of EX4 weapons and boss was melting during the first few mechanics despite damage downs or deaths. So it really does depend a lot on the group. Some of your parties probably didn't even get EX4 weapons.
Am I supposed to use food or pots on it?
I'd suggest doing that. Bring all your advantages to the table and don't hold back.
you want to trick people into thinking they can clear the content but you only want so many clears.
The savage clear rates are pretty high though. The last tier was cleared by over 50% in JP and over 30% in NA. I don't think they desire anyone to be unable to clear, but it is very frustrating in PF where your skill alone isn't enough and you have to rely on 7 potentially not-good players that are holding you back. The game design could be better, but a lot of people do it despite these issues.
If I suck, tell me so I can stop wasting my time and the time of others.
Well firstly, Stone Sky Sea gives a basic indication if you can do your base rotation. Being unable to do that suggests a fundamental issue such as breaking combos regularly or something. Then if you've gone through the list I made and are doing that, then it's probably not you that is preventing the clear.

SE intends players to interact with eachother and socialize. They say this occasionally when they release new rewards. "Ask players around you for hints about where to find it" (obviously people will just ask their FC or google it), but that's SE's intention, to get you to participate in the social fabric of the game a bit.

In this case, you can look up The Balance that give optimization advice. If you're following all that advice then, again, it's probably not you that is preventing the clear.