they require pretty much the best crafting gear you can make with optimal melds + food. Control specifically needs a lot of melds, but you don't necessarily need to be "fully melded" you just have to cap out how high you can meld Control/Craftsmanship for each item (or at least get close to it). I believe any lv70 items you get for your crafter can't be melded, so you don't have to worry about those pieces.