I use shrinkwraps as well a lot. Really in my opinion it will depend on two things.
1) how big the file you are trying to shrinkwrap, the bigger the file the longer it will take
2) this is the most important, the quality level, the higher the quality the longer it will take. I typically keep my settings very low to save time and i generally do not do anything else while shrinkwrap is running.
as far as i can tell from looking at the menu, i do not see any differences between wf3 and wf4 shrinkwrap.
also i am running the same system as you.
PS one more thing you can check are you display settings. if you go to view/display settings/model display tab over to edge/line if your edge quality is set high or very high this will effect it as well if you tab over to shade the higher the quality number there will also cause some freezing on really big models.
generally as a rule of thumb when i do full engine shrinkwraps i set those settings as low as possible, and then i have to play with the shrinkwrap quality a little to make sure it comes out right.
hope this helps.