when i run prot pally, I do a sizable pull, i BoP the healer, make all my friends then hit divine shield and do some work.
I would think BoP is primarily for yourself as healer but as a last resort for a dps. and only ever on the tank when in an intermission and the tank has some kind of massive bleed/poison that you can’t otherwise get off for some reason. but I would have to think that LoH would be much better for the tank.
again it seems best saved for yourself, since you can brez a dps or tank if necessary. if you are running higher keys and/or doing big pulls, you can cast heals as you want to keep everyone up and then BoP yourself to make sure you don’t die from healer aggro.