I actually find Garuda to be the hardest of the EXs. I was stuck on her from 2.1s launch until about three weeks ago.
1: So much crap going on. Even Titan with the Gaolers is a simple "gank tank and spank adds" phase. With her you have 2 tanks trying to tank 2 adds and play Voke Hot Potato with the Spiny at the same time, while the field is cut off by AOEs, the healers are getting pelted by Friction, and the MT is constantly on the verge of being oneshotted by DWW.
2: Hate is WONKY in there. I tried my hand at tanking it over the last couple nights. Defiance up, 2 FULL BB combos on Chirada during the tornado phase. Switched to my second bar to Flash the spiny I had just voked, and while GCD was ticking Chirada made a dash for the healers. All the tomahawks in the world couldn't get her back, either. That happened twice. I will never get mad at the OT in there again.
3: Its hard on healers with the AOE Friction damage and interrupted casts, plus the slightly random and nigh-undodgeable rain of feathers that causes Wind Burn that has to be removed, lest ir wear down DPS, tanks, or kill SCH fairies.
4: The weird lag on the spiny bubble that will randomly kill people even if they were the first one inside. Sometimes I get it, sometimes someone else. On every spiny kill it seems about 50/50 that somebody will get greased because it didn't register.
Ifrit is a bit of a pain because of the final DPS race and the massive AOE damage you get from the big nail kabooming. I wiped a few times because of bad timing: At 2 stacks tanking, big nail dies, and Sparky uses fire breath right after and kills me instantly. Or the worst one, when you clear the nails and both healers die to hellfire/plumes because of low HP and/or derping trying to heal others.
Titan's a chump. He's just as predictable as his HM version, and a half decent OT makes the gaolers a complete non-issue. His biggest threat is Upheaval, IMO. Been scooted off the edge a few times when the tank didn't have him pulled close enough to the opposite edge. I'd rather fight him twice than Garuda once.