Originally Posted by
Biomega
Because they're different forms of content. That was the Kara experiment - turns out, it works a lot better as a dungeon than a raid.
Also, I didn't say 10-man wasn't possible in parallel with 20-man, every now and then. Just that it's not a viable replacement, because it has too many design constraints.
And there's a reason for that. It's easier to make challenging 5-man content and 20-man content than it is 10-man content. It's no surprise that there'd be an awkward middle; that's fairly common. Too big for a dungeon, too small for a raid, no real place in between that is sustainable. In PvE, that is.
Or what are you suggesting that is meaningfully distinct from dungeons OR raids in some way? Is there some kind of unique design element you're proposing that makes 10-man work?