Pretty much... if you do things really quickly after a target switch or focus switch, it gets the old target.
You need to wait roughly double your latency, for things to update.
More then that, if Wintergrasp is in session on the server.

If you have 300ms of latency, and switch targets.
It is 300ms before the server knows you have switched.
And another 300ms, before it lets the other toon know.
Or thereabouts.