So... the "Hearing Voices" quest. Just for my own amusement, I've run it a couple of times solo. I knew going in that it wasn't meant to be soloable, and had that confirmed rather more dramatically than I anticipated. At level 35, casting Fire on the bugs produced mere 200 and change points of damage on each bug, and appeared to move their health bars less than 10% each. I'd read up enough beforehand to understand that SE's intent was that we bring a party, but the fact that I barely scratched the bugs is a matter of some concern. Even if the bugs didn't wear me down over time (a very *short* time, mind you; they do a considerable amount of damage with their attacks), I wouldn't be completely surprised if I ran out of MP before I managed to kill a single bug using just single target Thunder and Thundara (as opposed to the more expensive Fire and Fira).

Are they ever solable as a THM? If so, at what level?

And assuming that they are soloable, what about the follow-up quests? Are any of them soloable as well (aside from, obviously, "Gearing Up")?