Yesterday I learned about a fast way to run Missing -- if you are willing to forego Burno Vass and Guard Prosser optionals. After getting Evidence 1 (bill of sale) do not proceed to the playground, but return to the canal and swim west. There you can collect Evidence 2 and 3 with relatively little fighting -- a few mind flayers and Taken. We ran the quest several times in this manner; two times we killed Pale Fire, but it was by choice -- it is entirely possible to stay away from her.
So my question is -- can a rogue at level solo this quest in the above manner without alerting anything? End fight cannot be avoided, of course, but aside from that?