If you're developing your application using struts you should already noted this. There is already some comments about this on Tracker Issue #12308 .
As a way to help you people who are having the same problem as me, attached to this post goes struts tag library descriptors updated to use the JSP 1.2 syntax. That way IDEA can correctly parse them. Also attached goes the XSL template used to generate the TLD's, modified from the one that comes with struts source distribution.