Basically? No. There is a 75 point passive in one of the Thief constellations that will improve chest payouts, but that requires a minimum Champion Rank of 224, I think. There's another 10 point one in the same constellation that you can unlock around CR 29, that will improve your gold hauls.
Other than that there is no Luck stat you can manipulate.
This doesn't work for finding motifs/recipes as my Imperial toon has the worst luck in finding(farming) these out of all of my toons. I dunno if it translate in dungeon loot but am guessing it's pretty much the same RNG...