This is one of the most disappointing features I've found as a tailor/blacksmith. The only current use to these skill lines is the set bonuses.
The difference between crafting a vet rank 1 armor set and a vet rank 5 is marginal. In fact, if I want to craft a blue set, it's a complete waste of mats!
The majority of stats actually come from enchanting, which completely devalues the worth of tailoring/blacksmithing outside 6+ trait set bonuses (which still comprise a smaller percent contribution of your damage than the raw stat boosts from glyphs).
Every level increase, and even quality, is a measly armor increase. 100 armor difference is nothing, some of us can easily cap already with spells.
And a major design flaw is that the real difference comes from legendary quality. It should actually be the opposite. The later tiers should confer the smaller boosts for min maxing, but the largest boost should be in the intermediate tiers of quality. Otherwise there's no point in upgrading your armor quality unless you intend to go full into legendary.
There is virtually no purpose whatsoever in upgrading from green to blue, and even purple quality is not even that much of a jump. You basically craft the minimum level armor for each glyph level range, without any incentive to upgrade until vet rank 10.