I just completed Dragon's Hoard, a 20 minute challenge and received 5,669 xp.
For those math-savvy out there, that's a bit over 250 xp/min.
Now, I did run it more for the ingredients than the xp, but this is just plain laughable. I was level 18, running at CR 20 (because I thought, hey, it's more xp isn't it?) and it actively feels like I am punishing myself trying to get the House C gear rather than a fun alternative to traditional questing.
Whatever adjustments you made across the board, you are overlooking the appeal these challenges used to have to NON-EPIC players to fill in GAPS YOU YOURSELF HAVE NOT with quests that, you claim, are "coming soon". And I can even understand the nerf to certain Eveningstar challenges, and some 5 minute challenges to a certain extent, but the xp on the 10+ minute challenges is so absurdly low it feels like punishment running them at all, let alone multiple times for desired gear.
It feels like you used a sledgehammer on challenge xp with no real understanding of the impact it has on the longer challenges. The solution wasn't to nerf all xp into oblivion, it was to lower the 5-minute gains to be ON PAR with the OLD longer challenge xp. All in all, 1k xp/min is a fair benchmark for challenges I think, and I dearly hope the developers are not "done" with their tweaks to challenge xp. If they are, they've just made another trap of an adventure pack for the ddo store.
-TcJ
Edit: I feel I should also mention that I solo 3-starred the challenge. Not a perfect run, but a pretty good one for that challenge when doing it solo.