Should all my characters have use DoH and gathering?

[FoxyAreku]

You need to max all the crafting classes on one character for cross class skills if you want to be a competent crafter. If you don't care about that though I don't see a problem with what people have already suggested.

[Taika]

You need to max all the crafting classes on one character for cross class skills if you want to be a competent crafter. If you don't care about that though I don't see a problem with what people have already suggested.

This. If you want to be able to craft high quality items reliably at higher levels, you will need to have all (or most) crafts to level 50+ on one character for cross class skills.