I'll cover drop rates later because I want to talk about that separately.
Loot availability
So, to reiterate about the loot availability in cotw (ie what items are on offer)... I'd recommend looking at what drops if you're wanting to maximise your time against item acquisition and pick a group based on what items you need for the classes. But I'd say that is true for all group instance zones, really; none of the group instances on THF will yield a lot of useful loot on every run for every group member.
So you're right that you'll gear up more characters' missing gear in dsk but that is understandable; it's a raid zone, it should be a primary source of gear. It would be wrong if you could get all the gear that's available in dsk by doing a group instance.
But, and I get the impression you may have missed this key point, loot availability between the two zones hardly crosses over at all...
Of all the 50+ items you can get in cotw, maybe 8 of them have a direct equivalent item in dsk. That's roughly 40 items that you can get in cotw that have no T7 equivalent. In that list is a lot of slot 8 augments, as you did point out, but you may not know that you just cannot get anything similar unless you go back to t5/6. There are also several focus/worn items that just don't exist at all in Dsk, including no leg items at all. So I'd suggest checking what you need specifically, looking on alla clone and focusing your effort into whichever of the two zones has the items you specifically need. It may be you don't need any of the items in cotw and that's fine.
Item rarity
So item rarity. We didn't want to make cotw the type of zone you can do 4-6 times then forget. That's it basically.
That said, I appreciate that it's not going to be much fun if you get the ranger belt, mage bracer, bard boots and beast lord arms frequently (particularly if you don't need them).
I'm considering an alternative but it's the same in Dsk if you look at the similar items there. And, at the end of the day, Everquest has always had this "fun feature" where stuff you don't want drops

We can definitely review the drop rates at such a point that players actually run the zone more than a couple times and give feedback about specific items/npcs. I appreciate that you may not have a specific need to do this based on what is on offer, though.
Thanks again!