Well, I'm doing Dragon Hatchling and Dragon Lord Hatchling bestiary in Razachai Palace on the +2 and +3 floor counting from the lowest level. There are two rooms, where we can find a lot of them. Just enter these rooms, UE and everything is dead :D
Generally for me +2 and +3 is quite small area and we've got there such a lot of different monsters, like: Draken Spellweaver, Draken Warmaster, Draken Elite, Draken Abomination, Lizard Zaogun, Lizard Chosen, Dragon Lord, Dragon Lord Hatchling, Dragon Hatchling, Wyrm.
Similar to west Oramond are raids in Oramond's Factory on -1, just a little bit harder.
Good room with a lot of monsters is on Dharalion's respawn too - 4x Elf Arcanist, 6x Elf Scout, 2x Ghul and Demon Skeleton. UE would kill it all.