Titan requires some maintaining using E4E and Sustain. It helps to use Vitality accessories before summoning him but you can't zone or use Spur/Rouse or that'll reset his stats (if you swapped back to INT accessories). Ifrit is squishy yes but if you Place him in a segment around the boss where he won't get roflstomped by things then you're golden. Garuda is fine, she takes AoEs like a champ (like the T7 "donut" explosion which can oneshot a player stupid enough to stand in it for too long)

All in all this subject's a dead horse that's constantly being beaten. SE is already going to address Ifrit's unpopularity when they rebalance the Egis for the additions of Ramuh and Leviathan Egis.