The red mage solo aspect of the game is a very interesting one. You can't scientifically evaluate a lot of this stuff because the game kept changing. For instance Seiryu was not solo-able when it first came out, but with the addition of enough macc gear to land bind consistently it was solo-able for awhile. SE stepped in and added gradual bind resistance and it wasn't solo-able again. Then with enough added inventory for remedies and even more macc gear it became solo-able once more in WOTG.
For a lot of this stuff there's no way to tell where exactly the mob is and where the player strength is along the timeline. I hope this thread catches on and some people go out to see exactly where rdm is matching up against a lot of this stuff. Things tend towards the difficult side on nas, especially now that field satchel removal puts an upper limit on how much medication you can carry. Good luck out there testing the limits of what is plausible.
All that said a friend of mine and I did go back in the 99 cap to do some experimentation of just how strong red mage got by the very end of the 75 cap era. With out-of-era changes to enspells, ws functions, and Poison II damage (which we couldn't control for) we discovered most of the old avesta solos were playfully easy; however we were able to discover some interesting things about red mage's capability of solo holding HNM. You see in retail (and on nas) it is occasionally necessary to hold claim on an HNM while you stall for time as the shell arrives. It was very hard to get definitive data on how strong red mage was in these situations because on the off chance you were actually holding alone, by the time your first shellmember arrived (usually around 12 minutes) you weren't holding solo anymore and it cut the experiment short.
In 99 cap retail though we were able to go back and tune up a "best possible" rdm with a gear/augment limit of march 2010. We discovered a few things very interesting.
1) The TOAU hnm were all able to be solo-held for over an hour. Cerberus was the hardest, Khim was the easiest.
2) The flying COP wyrms were able to be held in the half-hour range, the limiting factor often being adds.
3) Ixion, Sandworm, Fafnir and King Behemoth were all solo-holdable until they raged barring unusually bad luck.
4) Jailer of Temperance, Jailer of Faith, and Jailer of Hope solos were all possible on extremely lucky runs
5) There is no world in which Byakko is soloable under 75 cap.
Hope some folks out there found some of that interesting. I've included a ~24 minute Tiamat solo hold video for viewing pleasure. Clock starts when the mob is claimed and ends when the mob is unclaimed (which, in retail, means you cannot cast on adds that aggro you).
https://youtu.be/z2Zg0NVqXds