Of course you do pitiful damage, because you're a level 80 that unequipped all your gear, your pitifully small stats are getting annihilated by the AP function lvl scaling variable. That 323 STR you had is only 1/3rd of its actual strength post AP calculations. But:
a) you aren't wielding a level 1 weapon in Sastasha in actual content.
b) your weapon damage is already synced to what's acceptable for the dungeon anyway, so it's not like you're getting any advantage compared to anyone else. (hence my point on why its irrelevant; it affects all your skills the same way0 so its a static variable in any damage calculation between rotations & skills, WD won't suddenly make a 400 potency attack do less than double that of a 200 potency one.)
But that's not even the point. Here's the damage formula for FFXIV:
Direct Damage (D)
D1 = ⌊ Potency × f(ATK) × f(DET) ⌋ /100 ⌋ /1000 ⌋
D2 = ⌊ D1 × f(TNC) ⌋ /1000 ⌋ × f(WD) ⌋ /100 ⌋ × Trait ⌋ /100 ⌋
D3 = ⌊ D2 × CRIT? ⌋ /1000 ⌋ × DH? ⌋ /100 ⌋
D = ⌊ D3 × rand[95,105] ⌋ /100 ⌋ × buff_1 ⌋ × buff_2 ⌋
I could go into ultra depth and breakdown every single step and variable, but it's irrelevant when there's only one I need to talk about. You see that Potency variable on the first line?
It controls the base damage that then gets multiplied all the way through. You could solve every other variable in the entire equation but change potency from 200 to 400, and the final result would be double damage. A better way to look at potency is to assume 100 potency is base damage. Then, take any abilitiy's potency and / 100, and that's literally how many more time damage you'll do. Like, this isn't even a debate.
To even show you my point, I went into Sastasha, lvl 80 WAR, lvl 1 axe, no gear, same setup as your level 80 PLD, lvl 1 sword.
That 120 Total eclipse potency you did equaling 45 damage? My WAR's decimate did 106 damage in the exact same scenario (about 2.1 times as much damage...curious; 250 potency is also about 2.1 times as much as 120 potency...hmmm). His chaotic Cyclone will do 300 damage (Chaotic cyclone post DH-CRT is 720 potency; 6x as much potency, and also close to 6x as much damage...it's almost like there's an extremely obvious pattern going on here). My heavy swing did 77 damage in Berserk. My inner Chaos did 637 damage. You can set WD to whatever the heck you want, potency is the ultimate variable in the damage calculation. A 400 potency attack will deal 2x as much damage as a 200 potency attack, it's pure, cold, uncaring numbers.
Dungeons are designed for certain WD ranges, hence why they nerf your weapon down to the WD acceptable for that dungeon. They are NOT designed for characters that can deal literally 3-10x as much potency in the same number of GCDs. Chad will still be utterly crushing Billy into the ground, it won't even be a remotely close contest. While Billy will be doing 77 damage Heavy Swings in berserk, Chad will be doing 640 damage Inner Chaos's, and his IR will be filled with 425 damage FC's. When most enemies in sastasha have about 800-1000 HP....yeah. Chad could 2-hit kill a Sastash enemy synced while normally it takes about 2-4 GCDs of the entire party's damage combined. Once again, I need to re-iterate this is a WAR, not only a tank that does less damage than an actual dps, but is a slow, GCD bound one. NIN could literally delete an entire pack of enemies in 1-2 GCDs + OGCDs with the potency I was calculating on it before I stopped because of how hilarious it was getting.
You let level 80's use their full kits and they'll be unleashing infinitely more times as much potency as a level 30 can do, completely shattering any hope Billy has at ever obtaining parity with Chad, and completely destroying the purpose of the dev's intention with the level sync.
There is no system you could ever design that would allow access to a level 80's toolkit and allow them to maintain parity without making every single skill not found at that level non-existent (1 potency, 1HP shield, etc). And that's why you better get comfy, it's not changing. Period. They'll adjust the rewards on roulettes before they devote even a nanosecond of brain power to ever change their syncing system.
Credit to the Allagan studies and their lovely resource for the damage calculation formula: https://docs.google.com/document/d/1...4lP1ZE08/edit#