1. People spend a lot of time there waiting on others with nothing to do.
2. Adding this would allow players to stay active practicing their class before entering dungeons.
3. The area is already a mini-hub since it's a Sanctuary, has a Meeting Stone, and allows Duels.
4. These are the kind of minor improvements that make the game more enjoyable for everyone without risk of abuse or being considered game changing custom content.
Lastly, I find Target Dummies to be a criminally underused game mechanic. They are such a nice feature to have around and yet they're all buried in the back of capital cities. There isn't even a single Target Dummy in Outlands or Northrend (other than Argent Tournament Grounds). I'd love to see them in every popular town (Booty Bay, Gadgetzan, out in front of capital cities).
Soul Shards would be nice but that isn't the primary reason. Please explain why it makes no sense to have target dummies in an area where players can practice rotations while waiting on their groups.