Thank you for the write-up, it helped immensely going in and finding the place.
I find also: http://ffxi-atlas.com helped me lots in finding the actual location of the stairs room in Aydeewa Subterrane.
Also, the fleas have a set movement pattern, if you approach the stairs as detailed above, try to do so in the right hand corner and wait for fleas to bounce away. (You can see them though you can't target them.) Then drop invis, see CS and quickly put invis back up again. /ma "Invisible" <me> on macro works well, don't bother running up the stairs, they'll see you and aggro. -_-
*Note: Still not quite certain if these are sneak or sight aggro as I had both up until I went to the stairs* After which I aggroed because I made the mistake of running up them while the fleas looked faraway and didn't aggro. Could've stuck my buff.*
Other than that, depending on level, they can also eat through stoneskin pretty quick, so if you're a rdm chainspell > warp might save you.