I highly expect changes to be made once 4.2 goes live and they see how much this is going to hurt the majority of casual tankadins who arent going to do what a good raid tank would which is cap your block chance and in probobly 70% of the fights simply keep holy shield up off CD all the time; And in the other 30% maybe wait an extra 10 seconds for a forseable dmg spike.
The whole point is that the CD is useless unless your gaurenteed to block during the use of the CD.