Digging into the numbers more, found the refining formula.
Crafting
Basically it's something like your refining level /10 is a % bonus, then + the bonus inherent from items (steel has a -2% (YES NEGATIVE) chance) + the DIFFERENCE between the item crafted tier and the refining agent tier (re: Tier 4 flux vs Tier 3 steel ingots) which for some reason appears to be 50% for one jump.
So it seems you want to perhaps use your high level fluxes with your low level mats, perhaps, to get just more than double the yield rather than chancing it on the bigger tier items like oricalchum which probably have a huge inherent negative bonus yield chance and match up with the flux tier for basically no bonus to begin with.
Here's what it looks like at 154 smelting:
Starmetal ingots go from 5% to 10%
Orichalcum ingots go from a 0% chance to a 3% chance.
It may be close but I'm pretty sure the lower level crafting is where to dump your higher level flux, which sounds backasswards, but the net you'll gain is huge.
So if I made 100 steel with 100 green flux I'd net: 163 steel.
If I made 100 Orichalcum with 100 green flux I'd net: 103 Orichalcum.
63 steel is saving me essentially 240 iron ingots (960 iron ore) and 63 white flux (kind of)
3 Orichalcum is saving me 24 Orichalcum Ore + 3 flux, 6 starmetal ingots (36 starmetal ore + 6 flux), 12 steel ingots (36 iron ingots and ~12 flux)
For easy viewing:
960 iron ore and 63 flux
vs
24 Orich ore, 36 starmetal ore, 138 iron ore, and 21 flux
It's actually VERY easy to get high level ore so I'm 95% sure you go all in on your lowest tier mats for the biggest bonus and saving the VAST majority of your gather time. Just make sure to try and get XXXXX's Accumulating armor before you do (2% bonus yield per piece, 5 slots). That'll boost those numbers even higher, but not sure it'll even make a dent in the higher tiers.