I'm working on my THM right now. Banging out level 20 camp leves on 4 and 5 star, and when I run out I attempt very select level 30 camp leves on 1 star.
I tried camping open world mobs, but it wasn't worth it due to MP regen unlike my DoWs.
What I'm doing right now is trying to kill all the NMs I can solo on my 50 PGL... I walk around on my THM and kill a few things on the journey and then switch to my PGL for the NM kills until I get a drop, then I move on. While it's not as good XP as camping and definately not as good as leves, it's still productive travelling.
On leves I am getting about 3-5K each on the L20 camps and 6ish+ on the 30s, but there is a lot more death on the 30 camps and thus the time > reward isn't really worth it yet.
FFXI:Sylph - Perrin 75 Hume THF; Retired (At least from my use any way)
EVE Online:ScraperX; Retired
WAR:IronClaw- Peryn SW;SkullThrone- Grymloc BO; Retired