Its entirely possible to solo. I've done it solo as a prot paladin, but OH MY GOD is it a pain in the ass. You have to CONSTANTLY switch horses because they'll chain charge you blowing you up, and it took me close to an hour to just beat the horse event, constantly switching. That said, with bubble, bop, devo aura+plate armor, and loh/wog, you're in no real danger of dying if you get dismounted.
And as the previous poster said, they don't regularly despawn. I've had the encounter bug out a few times but its not huge, but it bugs out sometimes even when I two man it(which takes muuuuch less time).