Yeah have thief vision on all the time - it makes navigation easier and helps you spot the grates that you need to get through.

I agree it is a terrible part of the game but once everything goes right it is only a 10-15 minute section. If you need to watch a walkthrough on Youtube or something to do it - do. If you can endure it there are no other areas this bad.

One tip from me: make as many characters as possible immune to Fear for this section. One of the Shadows in there has 1 move that inflicts the entire party with Fear, and another that insta-kills anyone afflicted by Fear.