Should it really be this difficult?

[Ashkendor]

I haven't been to Thornmarch Extreme, but the problem you run into in DF parties for both Garuda EX and Ultima HM is that there's a hard DPS check in the form of an unavoidable full raid wipe. Too many of your DPS derp and bite it, you aren't making those DPS checks. Ultima HM's Ifrit phase is notorious for killing DPS and healers alike, and don't even get me started on the amount of crap that can kill you in Garuda... I've beaten Ultima HM in DF, but only after several tries. Garuda EX took a lot of doing for me to clear. Like, weeks of trying. x_x

The best I can advise is to try to find a couple of close friends or FC mates and put up a party finder for it. My first win in both of these trials was in a party built entirely from my FC and a linkshell that I'm in.