Thanks for the replies. If all the dungeons were always going to be of equal difficulty it would take a lot of the fun out of exploring them. Glad to hear that probably is not the case.
Actually that probably is the case. All dungeons are roughly tuned to your character's level. There might be some differences, and some characters might be better at defeating some types of enemies and not so good with others. But in general they are all about the same difficult.
Unless you use mods. The OOO overhaul mod makes dungeons very different in their level of difficulty. As well as, generally speaking, making the dungeons more difficult the deeper you go into this. Mods like OOO are only available on the PC.