With buffs, I would say back of apostate.
Without buffs, I would say dragon valley or front/middle of apostate.
I leveled to 58 in dragon valley getting coinc from the headless knights and royal cave servants. There is also another quest there as well you get from the guy at the entrance to DV. I got 14 enria one time from that quest, although it is very rare to get a material reward, usually just adena.
You could also try the front of Giants Cave. It's a good solo spot and you can start working on getting recs for your a grade.
One of the SK's and the DA in my clan have been living out on the Frost lake. I told them I was going to start routing their mail up there and was going to buy them parkas and ice fishing gear too.
Apparently the mobs are sword weak and drop herb thingies.
~M~
I haven't been out there in awhile, so I don't remember all the names. But the ones I do remember were all high 50's, low 60's. Frost Tarantula, Frost Yeti, Frost golems...lots of frosty things.
I did Forest of Outlaws, Dragon Valley, Forsaken Plains (the orcs, drakes and gargoyles) and the Cemetary/Forbidden Gateway.
I tended to avoid places where there were too many multi-HP mobs. Those are just an ss drain in my opinion. I also avoided places like the Giants Cave where you can get stunned or paralyzed quite easily if you have -5 Con or lower. Plus there were one too many social mobs there and the odds of aggroing the entire room through a wall slab happens more often than you'd think.