Eclipse: I can't get project dependencies into Tomcat - eclipse

Question

I am modernizing a project that's been built using Eclipse Kepler's Export control for a few years. I ran into issues trying to jump straight to my end configuration (Java 8, Tomcat 8, CXF, and using Maven for builds) so I'm trying to do it piecemeal, and I've been stuck for two days.
I am using Eclipse Mars.2 Release (4.5.2).
For historical reasons, I have two projects, MyImpl project with all of the business logic (which is also the client/consumer of a remote web service, hence the CXF), and MyWebApp, a struts 1 dynamic web project. Everything was good running in Java 7/Tomcat 7. I am trying to introduce Maven, first into the MyImpl project, then into MyWebApp project, and finally building the web service client code.
I rearranged the source code to the maven way (/src/main/java, /src/test/java, etc.) Then I added a POM.xml with all my dependencies for MyImpl project. MyImpl project builds just fine, and MyWebApp project references MyImpl project in Eclipse, so that is good, too. Everything builds, no red Xs. Our test cases are, ahem, not well developed at this point in time, so I can't run those.
When I try and run on Tomcat 7 inside Eclipse, the Servers tab shows MyWebApp project under the Tomcat 7 server, but it does not show MyImpl project under MyWebApp project, as it did before. Yes, Java Build Path/Projects shows that MyWebApp project depends on MyImpl project. Otherwise it wouldn't build.
Tomcat fails to start up with a NoClassDefFoundError:
Jun 08, 2016 4:48:55 PM org.apache.catalina.core.ContainerBase startInternal
SEVERE: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/WebStarWebApp]]
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:188)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1123)
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:816)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1575)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1565)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/MyWebApp]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
... 6 more
Caused by: java.lang.NoClassDefFoundError: com/mycompany/mygroup/myproject/common/util/DB_Exception
at java.lang.Class.getDeclaredFields0(Native Method)
...
DB_Exception is defined in the MyImpl project.
If I double-click the server, click on "Open launch configuration", click on the Classpath tab, I see the JRE System Library under Bootstrap Entries, and bootstrap.jar, tomcat-juli.jar, and tools.jar under User Entries. If I add MyWebApp project to User Entries and start the server, I get a class loader exception:
Jun 08, 2016 5:20:54 PM org.apache.catalina.core.ApplicationContext log
SEVERE: StandardWrapper.Throwable
java.lang.LinkageError: loader constraint violation: loader (instance of sun/misc/Launcher$AppClassLoader) previously initiated loading for a different type with name "mycompany/common/logging/ISmLog"
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
<stack trace through initialization code>
at org.apache.struts.action.ActionServlet.initModulePlugIns(ActionServlet.java:1158)
at org.apache.struts.action.ActionServlet.init(ActionServlet.java:473)
at javax.servlet.GenericServlet.init(GenericServlet.java:158)
at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1284)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1197)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1087)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:5231)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5518)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1575)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1565)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
If, instead of adding MyWebApp project to the run configuration, I only add MyImpl.jar (digging into the MyImpl project, selecting MyImpl\target\MyImpl-1.0.jar), I still get a NoClassDefFoundError:
Jun 08, 2016 5:32:07 PM org.apache.catalina.core.ApplicationContext log
SEVERE: StandardWrapper.Throwable
java.lang.NoClassDefFoundError: mycompany/myproject/logging/InstrRecord
at com.mycompany.myproject.struts.plugins.MyImpl_PlugIn.init(MyImpl_PlugIn.java:55)
at org.apache.struts.action.ActionServlet.initModulePlugIns(ActionServlet.java:1158)
at org.apache.struts.action.ActionServlet.init(ActionServlet.java:473)
at javax.servlet.GenericServlet.init(GenericServlet.java:158)
at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1284)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1197)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1087)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:5231)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5518)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1575)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1565)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassNotFoundException: mycompany/myproject/logging/InstrRecord
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
This is with a brand new workspace and a fresh import of the code base.