Vardo auctions really depend who is there. Most everything at the auction Maria went to last time went for far less than what they would have sold it for normally.
As for the dungeons, I haven't seen anything over mid spawn in the vallaki area since the DMs stopped manually bumping the spawns after that "bug" we had. Most of the dungeons in game need to be made harder, really, the mid level ones can all be done by level 6 characters at the lower spawns.
Maria was soloing scrags at 6th on low/mid spawns, and could solo max spawns at 10th.
Purple she could solo on max spawn at 10th.
Max spawn werewolves at 8th, though, to be honest she couldn't kill werewolves at all until 8th.
Shadows, again, she couldn't hurt until 8th, but could solo any spawn after that.
Vampire crypts, due to her spells, she couldn't do until 8th, and couldn't solo a full max spawn until 14th.
Silver mines she started soloing at 6th, though it got progressively easier at 8th and 10th. The top two floors could be soloed at 10th easily, the bottom floor is still dangerous to try even at 18th.
Spider Caves, she started at 8th, easy to do at 10th.
The lich tower is still tricky for summoning based characters, Maria would have been 13th before she could solo max spawns there, and by 13th she'd stopped soloing all but a few dungeons.
Considering clerics are more powerful at the same level as sorc's, there are undoubtedly characters doing them at lower levels than that.