First off, to answer the over all question, I am a firm YES on this idea. I love the fact that you are bringing this to us in order to get feedback and suggestions. To me that basically says that it's not a question of "if" but "when" you will be going forward with something like this, have an overall general to indepth idea of how you want to implement it, but are open to suggestions/need input before you finalize the exact system. While there are many things that need fixing yet, this is definitely an addition to the game that will bring life to the current player base and also be an attraction for players looking to return to the game or just new players in general.
The idea about the Valkor and Reklar pieces having specific tokens that drop off of them is a great overall idea. It makes hunting them not irrelevant while people just farm easier epics, like others have stated. I'm sure since you are making different tier soul shards making these additional 2 soul shards that drop specifically from these two epics shouldn't be too much of a problem. But again, that's me both assuming, and hoping.
To those stating that bringing back old items will "ruin" the market that there is for them right now, please tell me what exact market that is? There are so few out there of the ones that people have, and it's not like they have multiple is almost every case, so they're not being traded/sold. I mean, if I saw even a couple times a month something like that being auctioned or sold then I could see the arguement that there's a "market" for these rare, no longer obtainable except by those who already have in game, items. Bringing them back just allows the people who were not here years ago, or who took a multiple year break (about 6 year in my case) the chance to obtain them too. This, from the rarity I'm reading, is actually going to *create* a market for these items, in an indirect way (as long as the soul shards are not attuned).
Regarding lower tiers as well as regular named mobs in the T5/6 range. My suggestion on the shards here is two fold. First, the drop rate on all regular named mobs needs to be extremely low so that regular named mobs aren't just farmed. With this being said, there's also step two, which is needing epic mobs for all tiers.
The way I suggest setting up the epics for lower tiers so that they are not just farmed by higher level players is as such. Have there be an NPC that offers "quests" to kill epics. I suggests that the quests offered depend on either your current adv or your highest adv class level. This would do many things. I would prevent high level players just farming shards of every tier, it would create a market for players of all levels (again, provided the shards are not attuned) and it would really give new players immediate excitement and a way to make some money or obtain cool items right off the bat. It also creates a need for players of similar level across all tiers to group together for something which right now isn't needed for anything until the end of the game. (if something is too hard, most people just come back to it later when they're a higher level)
Anyways, I see a lot of positive that can come out of this as well as it just being the start of something that will continue to get better and better as it's a framework for new content.
Just my 2 cents, or 2 pages.....