Crafted armors/weapons are decent gear. But it's really expensive to craft. And because it's not BiS, it's not really worth investing that much to craft them.
But armorsmithing can be useful for other things than crafting armor. With master armorsmithing you can craft ceramium medals from fragmented ceramium. This gives better exchange rate than exchange quest in katalam/danaria camps.
You can also craft dmg godstones (405 dmg with 10% proc chance).
As for other professions:
Weaponsmith - myth weapons are basically same case as myth armors, but you can use it to craft material for extendable weapon (alternative path if you don't want to get DLR extendable).
Tailoring - myth armors same case as armorsmith, can also craft ceramium medals and dmg godstones (4050 dmg with 1% proc chance)
Handicraft - weapons same as weaponsmith, I'm not sure if handicraft weapons can be used to craft extendable weapon material. Can craft ceramium medals from mithril medals, power shards and fabled idians. Myth jewelery can be BiS in some cases.
Alchemy - usefull for consumables like scrolls and potions. Can craft composite manastone bundle and higher level manastones from lower level ones. Also can craft fine bracing water that gives shield that lasts 20s and absorbs 50k dmg.
Cooking - usefull for crafting food, beverage and DP jelly. Can craft adaptive idium crystals needed by other crafts.