I think since the Hangouts migration I no longer receive Google Talk messages that were sent to me while offline. This is infuriating for me (and my friends). I'm unsure if there is actually anything we can do about this, however.
I noticed that this only occurs when receiving messages from Hangouts users. If an XMPP users sends me messages, then offline messages work as expected.
You need to log in before you can comment on or make changes to this bug.