Sea of spores - as some one said before, good spot, not very attended since most players exp in DV and later cementary/fg
Dragon valley - look for remoted parts of it, with difficult acces to other players, good spot is, right next to Ishka, not much moobs, not agro ones, for any nuker just get support and you'll get fast exp without any problems
Forsaken Plains - move your char to very north - south part of that location BUT not under GC, just next to it. Not many moobs, some obstacles, peacefull and quiet place for your L2W
Valley of Saints - like before, avoid places of quest, put your char into remoted region from barakiel
I tried to put those in order of rising char lvl, hope you'll find it useful
Avoid as much as u can quest related areas, as for sure they are/will be attended by other players (BS for example)
For high lvl exp, I would advice Swamp of Screams - especially for the WK, Destro, Tanks (blunt weak point, moobs in big groups, 1/2 hp, nice drop & spoil) I know it's hard to set up program, but i know that some ppl had worked it out.
Hope it'll helps, cheers