From my experience: the low lvl dungeons
Grimiska cave, lvl 2-3 max solo or party (i would suggest at least duo because of those pesky stunning arrows)
From what i understand the difficulty of the Morninglordian crypt was brought way down recently, classing the dungeon into difficulty lvl 2-4 (soloable for most i would summarize) For such a big zone i would rather see the second level be a tad more difficult (the mummies were great honestly) because the step from that to the undercity is a HUGE drop, very painful for lost low levels. A semi hard buffer zone between the two zone was a great idea.
And the difficulty of the thoul cave was brought up with the addition of the warchief (with a wooping +12 ab) and the elite hobgoblins, which was discussed on another thread, didnt yield enough XP for the challenge, up to difficulty lvl 7-9 (Party, i wouldnt solo this)
Zeklos crypt, a party of lvl 2-5 can do it easily and fast, but i've soloed the place with my rogue quite a few times from lvl 2-5 with a crossbow (gotta love them long corridors)
Beetle cave, yield a lovely challenge for a party of lvl 4-6, good xp as well, perhaps the best balanced low level dungeon.
Gilos, the great equalizer, depending on the spawn, a party of lvl 5-10 (bard lvl 8 can solo btw), only allips (and up) and gilos yields good xp
Shadow forest, lvl 5-6 party (i wouldn't solo this unless i was a bard) at the lowest spawn, up to lvl 10 with greater shadow fiends, still yields good xp
The orphanage (soloable by a bard lvl 8 again), can be quite difficult, perhaps the hardest of all low level dungeon, hag bulls and wolves yields good xp up to lvl 6-10
I would reconsider the Morninglordian crypt and the Thoul cave, perhaps need a bit of tweaking but beside that it seems pretty good