This is the normal behavior. we have the same issue here.
Once you go beyond 1,500 items, normal work in our case, each WS related operation take ~ 30 sec...
We had some sessions with PTC development & TS and as it seems todayRami
Have you noticed any increase in performance with larger workspaces since you wrote this? We constantly work with 4000+ workspaces and are having the same issues. We are running 10.1 M050.