The reason Shard of the Dead content is on a special shard is because we can do crazy stuff that you could never get away with on live shards. Also Shard of the Dead is done on our own time not during work hours. This means we get absolutely no time from QA (testers) to test our work. We essentially have to test our own stuff which means its generally going to be much buggier than content we release for our live shards.
Oh yea and don't worry there are no glass swords this year.