Hi, Dervy here.
What on earth are you talking about?
I know exactly how Determination Scales. I know the exact formula SquareEnix uses for Critical Hit Rating and Damage and whilst I don't know the exact formula of SS, I've nailed down precisely how it scales your GCD.
1) Stat-Weights will never be 100% accurate, of course. You're just stating the obvious here. Everyone should know this by now. If you're looking for 100% conversions, then you'll need to use Stat-equivalence. I refuse to use Stat-Equivalence, as many factors such as Job Rotations play a huge part in the performance of X Stat. None of those are factored into Stat-Equivalence. I believe, the exact ratios are something like:
CRT: 0.212 = 4.71698 : 1 STR
DET: 0.174 = 5.747 : 1 STR
SS: The JPs know.
They're strangely familiar to the actual weights I've posted for all Jobs... But, the Stat-Equivalence does not factor in things like Bootshine or Bloodletter, like I mentioned.
On top of this, amount of X stat you stack, will greatly affect the rate at which your stats scale your damage. For reference, here's a chart of CRT/SS functions on RAW DPS, without taking into account rotations:
https://i.imgur.com/xcZA9cO.png
2) What Job can't I do tests with, exactly? I can just "out-source" information from other players, and reference check them with all of my linear regressions solvers for inconsistencies.
3) No Stat has "Diminishing Returns" in this game. They have Marginal Diminishing Utility. Determination, Weapon/Magic Damage and "AP/MP" are the 3 main Linear Stats in FFXIV. Each stat will always scale exactly the same, per point, as the last point will, no matter if you have 5 of X stat, or 5000, each point will be valued exactly the same. However, the percentage growth (Utility), per point will decrease. This is what the graph looks like for Determination, all the way up to 3000. There's no fall-off.
http://puu.sh/oPRuN/2c6adee966.png
4) Even with knowing the formulas, the relative weights will always still remain inconsistent and never 100% accurate because the exponential growth of Crit and SS on gear, as well as the min/max allocations allowed on gear.
5) Elon, why are you on the aggressive towards JackFross? His knowledge of FFXIV is superior than a vast majority of players and he's actually studied Mathematics in University, unlike I have. He's corrected myself on multiple occasions.
Bingo. I had this discussion a few days ago with someone who does a lot of Monk Theorycrafting. Despite what the theoretical vacuum result of SS is, its potential is always tiered. Supposing in an encounter, you can do 100 GCDs in 4 minutes, putting you at a GCD of 2.4, or 625 SS. Any amount of SS you stack is wasted, until you can do 101 GCDs within those 4 minutes, or, you needing a GCD of 2.376, or 688 SS.
Which means, 62 points of SS are "wasted" and would've been better invested in DET or CRT, if you cannot hit the next theoretical threshold. This principle one of the many unfortunate fallacies of Skillspeed.
Though, this doesn't always reflect the exact performance in an encounter, as you'll never have 100% uptime to intensively min/max in this manner. If you have 0.5s downtime, when min/max'd at 688SS for example, that will automatically through you back into the 100GCD bracket.
So SS should be used as a rough guide to build your rotation and any left-over SS should be treated as a "filler", an aid, in case you mess up, or scrapped for CRT/DET. Example, a Monk at approximately 800SS can hit 11 GCD BFBs, so Monks should try to aim to build for 11 GCD BFB, then dump everything else into CRT, if they can. (For this patch of gear/raids at least)
Man, I could go on about this forever.