When could I solo crawl these dungeons?

[Izmael]

Karnor's Castle - doesn't really qualify as a dungeon. You can Jboots and train out, not to mention most of the time it's overcamped.

Howling Stones West - solo probably 58+ unless you want to struggle for no reason. Duo 56+

Velks - depends on area. Spiders: like 45+... Upper spiders including loot camps: 55ish+ I suppose unless you want to struggle and get your named pops stolen when you die to a charm break. Upper dogs: I wanna say 55+ but might be higher. Definitely 60 for some nameds. Lower dogs: 58+ I guess. Really a level 60 place. Broodmother: 58+ or so. Castle: never tried solo. It's an annoying place because of the traps, mobs have absurd HP and there's not much loot to be had. I suppose pretty close to 60.

Howling Stones South - HS south has trash mobs of level up to and including 54. Many of them casters and/or summoners. At 56 it's gonna be really tough solo. The best level 60 encs routinely die (or cap out) there. Just takes a couple bad RNG rolls on resists in a row and voila.

Dragon Necropolis - it has plenty of traps, so I don't know if any encs really crawl this place solo. If it didn't have traps and had at least some decent soloable loot thrown in, I'm sure this place would get a lot more interest.

Chardok - you can do the zone in to zone out run solo at probably 54... the mobs aren't too high and there are usually no more than 2-3 to deal with at any given time. It's gets a lot worse deeper in. I'm sure there are Chardok pro encs who could chime in.

Seb - the zone in to zone out run can probably be farmed for exp at 54 ish. I think the golems at the zone out can go up to 52 (I think sometimes they summon), but still doable at 54. Other places in Seb will require higher level and at 60 there will still be a ton of places you can't really crawl solo without struggling - all / most of the lower areas to start with.