Many thanks Raskah for the thorough explanation, I think I understand it now! Rather than consulting the Item Generation Tutorial I had been looking at the same author's Guide to Altering Items In Game, which has more of a summary of crafting so I guess it assumes more knowlege (which I didn't have).
My Strafer is almost done with A1 NM, I'll hire a might merc when I get to A2, then I'm going to give crafting another go after some LK and more Countess runs.
I don't have the option of a Windforce so I had been planning this char around Witchwild String. Unfortunately I only have one 1.10 version with the 2 sockets, and it's a low (152%) ED roll, so I'm not that enthusiastic about upping it. I'm aware of the Nef option but I wanted to save the sockets for Shaels or elemental damage jewels.
For now Lycander's Aim is more effective (no physical immunes yet so I don't need the Magic Arrow from WWS), I have two of those available and one has a good (196%) ED roll, so at some point I may have to decide whether to change my build plan. I could up the Lycander's and spend some skill points on MA and Crit Strike and swap in Highlord's Wrath for Cat's Eye. I'll probably end up running Hell Meph with a different char though in the hopes of getting another WWS with better damage...