https://eu.finalfantasyxiv.com/lodes...153483dbda9ea6

The Shadow DC was only really meant for people to use during the launch of DT as extra space in-case worlds got too full as they did with EW launch... A lot of servers had queues in the thousands at EW launch, they wanted to avoid that.

Their plan was to make a new temporary DC, let people travel to it and play on it while their regular one was full.