I don't think he wanted to do a full on farm group especially if he was new to the fight, so he probably tried DF first so he could test the waters and probably see the fight first hand. Most farm parties won't be receptive to bonus a majority of the time and every A4 farm I've seen, they usually solo heal. If 2 members went down suddenly then they were probably on top of each other when a Carnage Zero went out (I think thats the ability its been a while but its a target AoE and you can't dodge it so you want people to be spread out a bit). You'll also wanna be loosely spread for Judgement Nisi(hammer debuff) so that you don't pass it around and make healing harder. Helpful tip: 'Focus Target' Manipulator so you can keep up with which abilities he's casting.