When the augment slots were added to the game, you included a provision for rebuilding epic items to take advantage of the new slot mechanism over the old one. Which was a correct and just decision.
However, there is still a lot of gear that required grinding and luck to build. And a lot of that gear is pre-slot, but no method exist for upgrading, and thus it requires re-grinding and luck again. This is a poor design decision. There is no good reason someone should have to regrind for an item already possessed.
On the next update (or sooner), please institute a mechanism to allow for upgrading older named loot. And do so without adding odd or rare materials (no "You need to get this from that raid to upgrade" ****).
An example: Shields of Legend from the Necropolis. New versions have augment slots, old versions do not. We should be able to take an old SoL and toss it in a stone of change with some fragments or dragonshards and convert it to a new, slotted version.