I think they changed Main hand, off hand to the Quality/Quantity, before I believe it did vary by synth as to which one was more effect. Though I think the increase in "quality" for using the right tool is still there.

As to how Craft, M.Craft works, I always imagined it came down to the type of synth you are performing, so if you are making an axe it would be craftmanship, however if it was a wand or scepter etc, it would be M.Craft.

I can however believe this:
- Fire, Earth, Wind then the recipe is Craftsmanship
- Lightning, Ice, Water then the recipe is Magic Craftsmanship

Because you have something like Sarnga which uses wind/ice to make which would come from both sides meaning you would have to balance out both attributes to get the most out of it. It would be nice to get some confirmation on it all though since the information from crafting does seem to be outdated lol. Such as this lovely piece of outdated information lol
http://lodestone.finalfantasyxiv.com...e/craft01.html

Treatises
Some recipes will be accompanied with the name of a treatise such as Fletchery Training or Chainweaving Training. While synthesis can be conducted without first obtaining these books, the durability of the items used during crafting will drop significantly with each command. Treatises can be purchased in guildshops with guild marks.