For Ifrit fight, ya it's a dodge game. It's not about how much damage you can do. A group of people, with bad damage, can win it as long as they dodge well. (<--- I didn't define my "bad" here)

For Moogle battle, it's a damage game. You need nice DD to survive well. Moogle king will use something like Hellfire when he spawn, which is around 7 min you enter the field. the damage is based on how much little ones survived before the summon. The moogle will pop at each min. So, that means you have to kill one each minute. I think 2 moogles left already can wipe the most members in the party with sentinal on. all killed only get 200 damage with sentinal and 500 without. Then, you need a nice DD again to kill 8 of them one by one.

I think moogle battle is very stress on the gear. of course we also have lots case bad gear member out-damage good gear one...