Have you considered Dragon Necropolis? It's one of my favorite under-utilized Velious zones.
While it's not outdoors, it does have several large areas with plenty of mobs around to reliably pull. I wouldn't think line of sight would be a problem in the second large spider room, before you go downstairs, for example. Depending on how close you are to the 50 end of that 50-60 it may be a bit challenging, but by mid-50s I would think you could carefully (mind the traps) move to the lower Chetari city areas, which are both much more out of the public eye and probably have more mobs.
Failing that I'll echo Western Wastes as another zone I love from that expansion and spent a lot of time in. Could take some positioning and ignores to get going, and the pulls will be infrequent, but bear in mind the pelts and such off the wolves sold really, really well in that era, so that could make up for it. Same with the silks from those giant worms, though they are a bit nasty/annoying.