Indeed. I've seen claims that people have done a cycle in the Desert Highlands (there's an area where I think 3-4 spawn) and completed the achievement "quickly." Center north of Elon Riverlands has several that spawn in and around the passages under the earth elementals.
The Giants in Elon Riverlands in PoF are veterans but still count. I'm helping a friend with his quest to kill Giants and we can manage quite a lot there. They also tend to respawn faster there.
Struggled through it with core ranger. Killed all scouts but last one which made things more difficult. Downed a few times but rallied. Range helped me a lot.