I'd love it frankly if we went back to things like the 45 minute Baron run or Shattered Halls executioner run. Challenge Modes are the best things in the game right now, hands down. The rewards are a little thin, which is what keeps them from being as amazing as they could be. This is the content I want from Blizzard, not more progress bars to fill up via grinding.
And those are there for you, and I am sure more challenge mode dungeons will be added in the future, but, plenty of people (myself included) enjoy mindless grinding when we don't feel like doing something else. There is nothing wrong with options, hell, especially considering I HIGHLY doubt challenge mode dungeons are even that popular, and not for a lack of rewards, a lot of people just aren't capable or don't like them.