This is covered by this rule:
118.9. Some triggered abilities are written, “Whenever gains life, . . . .” Such abilities are treated as though they are written, “Whenever a source causes to gain life, . . . .” If a player gains 0 life, no life gain event has occurred, and these abilities won’t trigger.
Example: A player controls Ajani’s Pridemate, which reads “Whenever you gain life, you may put a +1/+1 counter on Ajani’s Pridemate,” and two creatures with lifelink. The creatures with lifelink deal combat damage simultaneously. Ajani’s Pridemate’s ability triggers twice.
Each Archangel sees two sources causing you to gain life, so each Archangel will trigger two times, for a total of four triggers. Your creatures will get a total of four +1/+1 counters.
Nathan Long
Wizards.Com Boards NetRep