INT or WIS - whichever is higher, affects tradeskills.
STR for smithing
DEX for fletching
This has been true on every 'classic' server I've played. Not sure about poison making. Keep in mind that STR/DEX are just additives - if int/wis is higher, it uses that.
Want to try it out? I have a spreadsheet. It's for JC. The formulas aren't that complex, but they do have some complexity.
https://docs.google.com/spreadsheet/...Wc&usp=sharing
Go here. Hard tradeskills have difficulty of 4. Others have 2 or 1, I suggest you look it up.
Put in your main stat (INT/WIS or STR/DEX for the others) and then your skill level. While the pricing information is not valid, all the trivials are still true, as is the chance to skill up and successfully make an item, assuming you have the right difficulty in there.