Currently there is no mouse decorator when dragging event dispatchers out of the My Blueprints panel in the Blueprint editor.
This contradicts the functionality of drag-and-dropping variables, functions, and events. Not a regression.
4.8 Binary: 4.8.0-2556684+++depot+UE4-Releases+4.8
Result: No indication that you're dragging the event dispatcher (via mouse decoration)
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-15930 in the post.