Well, it's entirely possible to use Rune Pulse without any addons/scripts or watching the buff bar:
Watch the refresh on your Rune Pulse button instead (the basic button you get from dragging skill book to hotbar). You said tanking, so I'll assume you're in Shield Form. And C/R, so I'll assume dual wielding. That means that the odds of Rune Pulse ready to use and Chain Drive NOT activated are really small.
Just click Rune Pulse as long as the button doesn't show a cooldown timer (you'll see the cooldown refresh whenever Chain Drive activates). Usually it'll work because Chain Drive. On the rare occasion it starts the 2 sec cast, move and push a different button instead. Maybe you wasted half a second on rare instance, but at least you didn't have to mess with addons and such.
DIYCE or other scripts are probably the superior option, but this method kinda works too.