I think Micah is saying that there's a valid reason why they
Eh. Most of the adventure was about them trying to get through a door.
As for enemies, the guards were fairly normal humans, outmatched by Holga. They avoided the intellect devourers, ran from the dragon and the displacer beast, and let Zenk handle the Thayan assassins. Sofina missed (definitely?) with her meteor swarm and then they ganged up on her and beat her with a magic-suppressing bracelet.
They weren't even planning on fighting Sofina in the first place.
If you accept that players don't need to have near-100% chance if victory, you can run these kinds of adventures at low level. If the players decide to go back and not only stop Sofina's plot, but decide to stick around and fight the 17th level wizard in melee, well, hopefully they have good dice. It's certainly not impossible to beat a lone wizard who relies mostly on evocations, but someone could die--fortunately you have a resurrection item right there.
I have thrown a tougher problem than this at 3rd level characters--they had a chance to back out but I was pleasantly surprised to find that they won, through smart play akin to Kira invisibly sneaking on the antimagic bracelet--and much tougher problems at parties of 5th-9th levels.
So no, this is still a fairly typical adventure for low-level characters (say a mix of 3rd-6th level) in my eyes. I'm prepping to run it for a bunch of starting characters in DFRPG. (Confidential wisdom is that DFRPG starting characters are somewhat equivalent to 5th level D&D characters. I would personally say 8th but most people seem to disagree.)