not true not true..
I've found a few places to hunt in the TS to hunt at 20 solo...
first go to the stepps station and go to that TS zone, I don't know where you'll end up if you take the zone behind the waterfall.
when you first get into the zone a little way you'll see quite a few strong group mobs.. follow the road a bit, being careful of undead of course and eventually you'll see a side-road heading off to your left..
at 21st level there were quite a few white / blue / and yellow con solo mobs with not a single aggro mob along the path.
if you choose not to make that left turn, continue down the road til you come to a tower on a hill-top, the road will make a sharp turn left and if you go right from that point you'll see destroyed farmland (and some STRONG undead farmers)
anywho, going to the left at that point will net you things that con'd white or yellow to my conjuror at 21st level, and again no high aggro mobs in the area... though this area is smaller than the previous one I mentioned as far as things to solo, it wouldn't be bad XP to make the run between the two areas. Clear one out.. move to the other while the one you cleared re-spawns.
I've not gone terribly much farther beyond this point in TS, only other area I've scouted is where the centaurs are which is farther down the road and over a bridge from the tower on the hill I mentioned.. not much to solo in that area, but it's good for resources due to the non-aggro mobs wandering and you'll have the occassional mob you can take down as well.