Lylirra replied to a fan question about Nephalem Trials, which were not seen or spoken of at Blizzcon, to say they’ve been put on hold for now.
The gameplay felt great and was in a good place at gamescom 2013 where we announced them – which is actually why a lot of the individual Trials have been added on their own as standalone events into Reaper of Souls – but the mechanism that made the overall system feel meaningful over a long period of time wasn’t and would take some pretty significant tech and time to implement (in this case, at the expense of other features as well).
Rather than delay the release of the expansion to make sure Nephalem Trials could make it in with all the necessary components, we made the decision to cut them for now and re-focus our efforts on making sure other key systems like Adventure Mode, Bounties, Nephalem Rifts, and Clans & Communities (just to name a few) are solid. It’s not an ideal scenario, but these are the kinds of hard calls we sometimes have to make in a world where we can’t stack +Maximum Resource. >.>
Check the Nephalem Trials DiabloWiki.net article for past blue quotes and datamining about what these NTs were going to be. Basically they were going to be rifts you found randomly through the world that would let you pass into a new level with some intense action — the Jar of Souls was the usual event cited for reference, with ever-increasing numbers of enemies. Presumably ones a lot more dangerous and numerous than the weak skeletons that the JoS throws at you.
I liked the idea and how they come back at some point, but honestly, there’s so much to do in Adventure Mode and with a whole new act and class that I don’t think we’ll miss them terribly at RoS’ launch. And when/if they come in a patch a few months later, it’ll be like a new thing! *acceptance*