I tried out plane of disease bugs near the castle solo at 70. They are super easy, only hit for like 357 max ( some do harm touch for 900ish though) and they give about 2% a kill.. some gave 3.. not that many.
I used to be a big fan of inner acrylia at 65 because of decent tribute and cash loot, plus it was 2% a kill (this was the common xp gain I saw in groups in most zones minus eps or better). The mobs in AC dont hit hard and its wholesale slaughter.
Thats pretty much what I found POD to be.. Easy Fast Kills for moderate aa xp gain. No real down time. Once you wipe out the umberbulks, just move to the light crawlers... wash, rinse, repeat.