I'm not sure what mine is, but I can get most DPS's I run with from near death back to full health with a breath of life. I mostly use it for those oh $#!+ moments when a boss catches the group with a big thump. Next time I run a dungeon I'll try and get a number.
Probably more important though is how many times you can throw it quick and still keep your magicka up. Spamming healing springs while throwing in shards and repentence as needed I never get below 50% magicka but when I have to go with the breath of life a few times I gotta start paying attention to resources. Usually I don't run out but some of those really long battles with the other group members scattered around so one healing spring won't get all of them can be iffy.