what stats do i need? what cross job skills should i use?

[Almalexia]

First, you don't need to speak for any record. There is a record already.

From the ARC thread:

After reaching a threshold of 280 Dexterity, adding any more dexterity (up to 325 in my data collection) appeared to add no damage whatsoever to Light Shot or Heavy Shot.

Also, similar to Dexterity, Piety seemed to “cap” at 280.

Seiken found that these two stats were capped. Not capped with diminishing returns, simply no returns at all.

Second, the increase of STR from trial 1 to trial 2 was 23 STR and of 2.79 average damage. The increase from trial 2 to trial 3 was 24 STR and 1.64 average damage. Hence, "~23 STR" for "~2 average damage"--an average of the averages to compare it to ATK. It is entirely possible STR has diminishing returns, and if I had more STR gear I could probe further, but that's not at issue here. What matters is that STR doesn't cap at 280 and gives returns on into the 300s, and ATK has even greater returns than STR.

Next, I stated at the beginning that my target was Lv. 52 Zaharak Halberdiers.

Finally, yes, the one thing you can fault me on is neglecting to mention my sample size. I generally do 500 hit (excluding critical hit) trials. Allow me to add that to my post to avoid further confusion.

I strongly advise against using gut feeling to judge character optimization. Eyeballing figures will almost always make you see things you want to see, and none of what you don't want to see. That's why we have parsers, and math, so we can know.