Just had a party by the outpost in Sanctuary of Zi'Tah, and wanted to make a couple comments.
Myxos, while of the appropriate level, have a nasty special attack, Dark Spore, that hit me for 423 and killed me. Of course I'm a Taru paladin with somewhat low HP, but it's something to be careful of.
Next, by the time we hit 39, most mobs were giving less than 100 xp each, with only an occasional gob pushing 120-150. I would say 35-38 is probably the best level range for here, though 35 may be a little early. 38 was easy fights with decent chain experience.