To be quite honest, I think the binding is probably the easiest route, however when I've been in that situation I've found composite components often offer a better solution than bindings. Depending on the situation (and again, its totally case by case) you can use a composite component to get around this problem. This allows you to reuse parts of a page creatively so that your specific updates don't take a lot of work and you can reuse the code.
An example of this might be:
//comp:myDialog
...
<composite:interface>
<composite:attribute name="update" />
<!-- Other attributes -->
</composite:interface>
<composite:implementation>
...
<!-- Implementation -->
<p:commandButton update="#{cc.attrs.update}"/>
...
</composite:implementation>
And here might be the component in use:
//for the sake of argument 'comp' as your library
<h:form id="someForm">
<p:inputText value="#{bean.changeMe}" id="changeMe"/>
</h:form>
<h:form id="dialog">
<!-- dialog here -->
<comp:myDialog update="someForm:changeMe" />
</h:form>
By separating this view into a piece of reusable code you might be able to get around the burden of specifying the full path because it is now much easier to reuse. However, I think it is a toss up of a binding or the composite component depending on the specific case. For reuse, make a new object (component) and reuse it. If you're dealing with a highly dynamic environment: bind it.
I'm not an expert by any means, but generally speaking the above has gotten me out of a lot of tough situations.
EDIT: on a re-read you should also make sure that the tab-view isn't lazily loaded and take a look at the rendering to make sure the path is correct (inspect the ID). I've had problems (in older versions of Primefaces) where sometimes the id was nested inside a p:outputPanel or in rare cases the subview id. It might be a very simple fix by specifying the full path ':subview:form:component' though that shouldn't be the case.