Your
WTF/Account/[ACCOUNTNAME]/[SERVERNAME]/[PLAYERNAME]/bindings-cache.wtf should be copyable to each character. Make sure that on the character though you have the use character specific keybinds checked off so it pulls from that and not the global ones. I checked the file just now to make sure it didn't have a character ID or something like that in there and it doesn't so just copying that into each characters directory "should" do it after that checkbox is marked off.