How to debug an hanging impdp importation
I got it to work with a weird fix : I removed the 'APPLICATION/APPLICATION@XE' and entered the username/password manually with the interactive prompt. 

I consulted this page: http://www.orafaq.com/wiki/Datapump and realized that I was not getting an equivalent of this line Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production, which tipped me it was a connection problem. By trying to remove the username/password from the command line it suddenly fixed the problem.

I am afraid I can't exactly say why this helped, but I hope this can be useful to someone.