The Tarkanna vendor wasn't (on PTS) giving out moddable gear.

300 tech frags for a non moddable chest / helm / etc.

The only moddable gear it gave out during phase 3 were the weapons / off hands.

 

 

The vendor that sold the set bonus armor SKINS (no mods, just the empty shell) didn't really have any RNG at all. What you saw listed for sale was exactly what you got.

 

The Kai Zykken vendor that has "rotating stock" of items for sale, those moddable shells to have the armoring / mod / enhancement RNG that you have to pay attention to.

For example...the format I use to keep track of the rating of the gear I use is 248/248/248 armoring / mod / enhancement.

The Kai Zykken vendor could give you armor with 276 / 274 / 270. The next purchase of the same item could get you 272 / 276 / 274....and so on.

That's only part of it. The pts vendor during phase 3 was giving out enhancements, are armorings, Hilts, barrels, and mods.

So if you wanted just to swap gear one for one you could get a random piece of gear, or if you needed a specific mod for a shower you can get that much specifically but it would be one with random stat yeah, but well within the gear rating that would upgrade you.