I think the whole PDC thingy is some real improvment. the infos about it are just not too much accessible, going to the top menu and finding the entry inside the popup. even impossible when the box is getting big.
I think that would be overkill to put on the device it self.
However, like plugins, the internal devices could get the “?” as well (if you did not know, hover the mouse over the “?” on external plugins and you will see the latency info).