No, the two are still separate ranks, with the Knight-Divine ranking above the Knight-Vigilants. The way Cassandra speaks of the Knight-Divine, I got the impression that it's not one single person but maybe a small circle of the highest command, like the three Talons of the Antivan Crows.
The Knights-Vigilant seems to be the internal auditors that overview matters before they get escalated to the Knight-Divine / the Seekers, and possibly lead the Templars in the absence of Knight-Commanders, according to what the sister says there and a similar line in... TME, I think. Anyway, as far as the internal audit part goes, you can find the body of one Knight-Vigilant at Therinfall who was to investigate "Lucius" and remove him from command depending on what he found, according to a letter in his office.
Quite, I believe the Knights-Divine are the highest Templars of them all, serving at the behest of the Divine.
The Knights-Vigilant are ever "vigilant", watching for abuses and the like.
On the Knights-Divine, yes, that is what DG says, that they run the whole thing and are a committee of folk selected by the Divine. My problem is with BW also saying "the Knight-Vigilant commands the templars."
I'm curious about this dead Knight-Vigilant then. Is there a codex entry or something on it??
(edit: Incidentally, no , there are no Knights vigilant or divine in either Asunder or TME.)