While I find the hole hospital complex quite fascinating I do not think a Otto Wagner nomination and even less a viennese art nouveau nomination should concentrate on this complex.
I agree Art Nouveau in Vienna would merit its own place on the WHS list. The problem with such an idea would be that most such sites are already covered by the two existing nominations. Otto Wagner's Majolikahaus (next to Theater an der Wien), Postsparkasse and Pavillon Karlsplatz as well as the Secession building are all part of Historic Centre of Vienna WHS. Wagner's Hofpavillon Hietzing is a part of the Schoenbrunn WHS. In fact Otto Wagner's only buildings not covered by current inscriptions are his own villas in Huetteldorf and the proposed hospital (Otto-Wagner-Spital) with Kirche am Steinhof.