why does it matter which PC the priest is on? where you using two keyboards?
I would think that you would only want to use one keyboard and if you need special keyboard bindings on the priest you could make duplicate wow directories and setup the special key bindings.
I think the keybindings are kept in the WTF directory, I think in vista (ugh) you can link all of the non-WTF directories to a common place so you only have to update one copy of wow.
X:\WOW1 << all warlocks with the same keybindings
X:\WOW2 << your priest with special keybindings