Bloated spiders can be found off the road to Keltoi. They only spawn at night, I believe, as I haven't seen any around that area during the day. They can be hard to find, especially with all the other aggro mobs running around, but they're in there. Undead druids and black dogs can be found at the glowing stone rings on the plains. There are about 3 or 4 different sets of rings, so you shouldn't have any problems finding them.
Laridia can be found around the corner of one of the buildings in Cotswold. Yes, that's outside.