Bloodthirst heals 384 for each target you hit with the combo. If you hit two targets, you heal the whole group including self for 768. The heal can crit as well, and normally heals 660 if it does. It can hit nice as well, the highest hits I have seen from it on my average geared Shammy is 2300-2350. It is also the only (?) combo that BS has that hits the right shield of the mob (left finisher).
Your Nature's Blessing heals you for 581.
Look for something like this in your combat log