(Eliseus reported for spam + Placed on ignore.)
Ifrit is more important on it than Garuda as Garuda provides more straight DPS time, especially if you're attempting to skip. But you do need more accuracy to hit the sweet spot regardless with Garuda, as she's higher evasion by and large with Ifrit, aside from Extreme which you said is a minority event anyways. I do have to give props that the developers are starting to realize they have to make mechanics that stress the importance of a balanced group.
Ifrit you want 100% simply because you don't have the time for extended combos. Garuda gives far better tells for her skills.
A side-note - I did state previously that I am not in a Hardcore shell so 'optimal build mention' is irrelevant to the discussion. The game is currently balanced around a party of the 7 base classes with 1 flex position - and they're getting better at putting emphasis on that. I'm hoping by the time they come out with Battle Regime again the concept of class stacking will seem ineffective by comparison, but that doesn't stop my approach.
Ultimately the emphasis on loot over people is the reason why I stay away from hardcore groups. They won't hesitate to marry you to a class or job that you don't enjoy because it measures out as a better job for the role. My approach is the inverse, you chose a Class/Job you chose to excel at and you focus on being the best it can - regardless if it's the favorite of the patch or not. Thus, my concern isn't the popularity of the job, but rather what I can do to make it effective. For Chimera, I might just go Lancer to equip Maim - (if I do the run at all, I don't think the shell is interested really. I am though, being told the job is unpopular presents me with a challenge.)
This means various builds for various fights, and looking for all the little quirks that can eek out a bit more performance.
You let the person come to their own conclusion of having more than one job available for the group - something that will get easier to do once Classes have more than one Job attached to them.