Has anyone tried this solo? I can't get the second half of the bridge to extend once I work my way down. Is there some sequence like Lumul-nar you have to get correct to have it extend?
If I understand where you are getting stuck, in the solo version you actually never have to cross that bridge. The bridge I think you are talking about extends half way after you turn a wheel and pull a lever just before it up a small set of zig-zagging stairs? Well, try this: turn that wheel, pull that lever, and run BACK the way you came in. There is a door that would have opened just back twenty paces once you turn left onto the walkway you just came in on (technically I think it is the wheel that opens it, but I'm not sure).
Go in that door, fight two mobs, and drop down a hole into some water. From there, you swim in the water to dry land, and continue along the walkways from there. You'll notice that you soon will get to that "half-extended" bridge just up ahead, and there is another lever that will extend the second half, but that doesn't matter because you won't need to go that way again. ((Note: I don't think you need to - or should - pull that second lever that extends that bridge, because I'm not sure if it does something somewhere else. I ran this the other night solo and never pulled that lever, and got through this instance just fine)) Your path should be to the right as you come out of the water, and then you will eventually fight another group of mobs, then descend down another level on your left.
Describing it in text sounds convoluted, but the bottom line is that you don't need to cross that half-bridge, but rather backtrack after turning the wheel/pulling the lever and go in the newly opened door.
BTW, in the group version, that door is on a short timer so one person pulls the lever while the other 2 wait at the door and enter immediately with the door shutting the lever-puller out. The lever puller goes down to the half-extended bridge, and the other drop down the hole and eventually pull the other lever to extend the second half of the bridge so the lever-puller can get across.