Well, if you are doing daily crafting writs on all of them everyday then yes. By learning all alchemy reagent traits, all runes, as much as possible purple and gold provisioning recipes and gear traits on each character you significantly boost drop rate of master writs. Motifs also boost this, but trying to learn more than some basic motifs on all chars seems not worth the investment.
IMO, no.
I do level all the crafting skills on all characters for doing daily crafting writs.
But learning all those styles no.
I think recipes, and furnishing patterns should be account wide.