tomcat8 - custom error page for 400
I also faced to this issue and as a workaround I implemented own ErrorReportValve by extending org.apache.catalina.valves.ErrorReportValve class and configured it on my Tomcat.
To accomplish this the following article was really helpful: http://robupcraft.com/tomcat-valves/
Note that for the implementation (and successful build), you need tomcat-catalina dependency.