After switching from Microsoft TMG to F5 and iApp "f5.microsoft_exchange_2010_2013_cas.v1.2.0" users no longer can choose "Light OWA"

You say you are using LTM v11.5, and NO APM ? Correct ?

If so, Im not sure what you mean when you say ... "actually don't get a page at all just the login"

I assume if you are using LTM only, you are load balancing to the OWA login screen ... which should still present itself in the normal way ?

Can you explain further ?