I tried with another person (he was monk and I was scholar) and we had to leave 3 moogles alive in order to survive Memento Moogle. I haven't tried on WAR but it seems it would be tight to get through the dps checks. I think it's quicker to get in a party with someone that doesn't have the same desynth as you instead of waiting 3mins before dying a few times just for the echo.