I remember back in BfA when I leveled through Eastern Kingsdoms for my first time. The existence of the Gnomeregan dungeon was in my mind since I did the Gnome starting area, and I first returned there at level 16 and entered Gnomeregan for the first time hoping I could solo it. Gave up at the first trash mob.
Later I got sent off to Northrend and quested through from Boreal Tundra and eastwards. By the time I reached Zul’Drak my level was about 85 while every mob capped off at level 80. Got yet another dungeon quest, and figured I might as well give Drak’Tharon a try.
Surely I wiped on trash, but I got the feeling that a couple more levels would make it a far more comfortable experience. So I returned after a few more dings and owned the instance. That first time feeling can not be described.
Deadmines long long ago I want to say level 35 or so on my hunter, I definitely remember doing it solo a couple times and then when I knew I could I would help run friends through.
Back in Vanilla on a level 25ish Orc warrior I found Razorfen Downs in southern Barrens.
Not really knowing what a dungeon was I thought I’d give it a go. I thought with a little CC and a careful pull I might be able to pick off the trash one-by-one.
Probably Deadmines or the Stockade. Except I probably didn’t solo it. I was probably carrying some random person in /LFG Chat who was looking for a group, because that’s what the community did for each other when they were bored, they helped people and didn’t expect any kind of payment for it.
Wailing Caverns.
I did that dungeon so many times in vanilla on this character and my alts that probably is the most run dungeon ever in ths account followed by Scarlet Monastery.
First it was because it was easy to get in to groups, later on was because I was helping others in my guild and afterwards alts.
Define solo, solo as in soloing a low level on, or solo a dungeon when it’s still valid content? I solo’d some bosses in Halls of Valor, to get my pet as a hunter when it was still fairly hard.