Phuabos drop like crazy. Just solo exp on the VT ones until you get as many as you need. You'll walk out with good exp.
Aerns are stingy as a mofo... You just have to deal with it and keep killing them.
The big xzomit's drop them 100% of the time. If you're soloing, kill off the small ones first then kill the big one when they're dead. If you're duoing, sleepga>killbigone>logoff works great or you can just kill them all.
Just have fun with hpemdes. Drop a drain on one and then kite it till it opens it's mouth. Then drop a Freeze II on it for a big 3k bang.
Yovra and Euvhi's are a bitch, period.
I solo'd 90% of all of my organs and tissues and collected the whole set (and relaxing earring) before I quit. It's a bitch, but it's worth it.
You could go with help for a better drop rate, but I just took it night and slow and considered it as several exp sessions. Feels great when you do it yourself, but most people probably don't have that kind of time.
Tissue drop rates are shit. When I did it, I tended to get about 8 organs before I'd get a single tissue. And then when I stopped needing tissues whatsoever, they seemed to drop every other mob...