Are there any blacksmith merchants who sell “master” level components

It gives set bonuses based on how many pieces you have, and doesn't always require completion to get the best set bonus possible. See my screenshot below, which shows one piece of the "Captain's" set.

• The area circled in green shows what types of pieces exist in the set (helm, torso, pants, gloves, boots).
• The area circled in orange lists the bonuses you'll get as you add more pieces of the set (so 2 pieces gives you +20% health, 3 pieces adds +20% mana, etc)

There do not appear to be any hidden "complete" set bonuses. So notice that while this set has 5 pieces, the set bonuses only go up to 4 pieces. Adding in a 5th piece has no special effect.

As it happens, by *ahem* leveraging some systems in the game, you can in fact turn a high-quality gem plus some low-quality components into a high-quality component that shares the attributes of the gem.

The TL;DR version is:

• Craft a junk item, but include a gem whose effect you want
• Salvage the junk item, and hope you get the effect in the salvage

The linked guide has a bunch of essential tables that describe how this works in greater detail, but here's the theory behind it and an idea of what you can accomplish with a bit of effort.

The method itself relies on two game mechanics: first, when you salvage an item, the game tries to give you pieces that could have been used to craft that item - and for whatever reason, it prefers to put enchantments on the item in the second crafting slot on the Blacksmithing menu. For instance: if you salvage a sword with a poison DOT effect, the game will prefer to give you a hilt with the poison effect over, say, poisonous rivets or grip.

The second mechanic is that by crafting a gem into an item - that is, by using the Blacksmithing rank 7 milestone, not via socketing - you imbue the resulting item with all the properties of that gem. This means, for instance, that if you craft a Gem of Winter into a dagger with a junk blade and a junk hilt, you'll get a junk dagger that nonetheless has the Gem of Winter effect.

Now, what happens when you salvage the dagger you just crafted? The game will try to give you components that could be used to re-create the dagger - but you'll never get a gem back from salvage, and the game vastly prefers to give you an enchanted version of the item used in the second crafting slot. That means the game will frequently provide one component: a Flawless Frosted Hilt.

Thus, theoretically, you should be able to create many kinds of Flawless components by gem-forging junk components and then salvaging the resulting item.

To test this theory, I crafted a total of six Azurite Daggers out of six small Azurite blades, six junk hilts, and six Gems of Winter. Their stats were nearly identical, differing only by 2 points of physical damage (I used some crude hilts and some basic hilts)

(the +5% damage is because of the Mastercrafting blacksmithing milestone)

Then, using the scientific miracle of quicksaves, I salvaged all six of them six times and recorded the results.

Those are pretty good odds, huh? It seems like if you get a hilt, it's going to be a Flawless Frosted Hilt - and there's a 50% chance of getting one.

Now, this method isn't quite as flawless as its results - there's all sorts of restrictions and rules that make things complicated (e.g, mage weapons and all three classes of shield can only be crafted with utility gems, certain enchantments don't apply to certain components so you can never generate them, and a bunch of other things).

However, with a bit of foresight, you can make something basically obscene. These guys took me about fifteen minutes and one quick load, and were crafted out of purely Flawless components (I got lucky with the Flawless Sustaining Binding). Keep in mind that the base damage is nowhere as high as it could be, since I only have access to Azurite blades.