So I made my character and dutifully started slogging through lands to the northeast, thoroughly investigating all previously unknown territory, solving every little quest (that I could find) and killing anything that moved (or at least, anything that attacked me). Eventually I ran out of quests soon after killing Warden Krieg.

My contacts in the starter town decided I should head to the northwest, which I did, and similarly explored all available lands, solved every little quest (that I could find) and killed anything that attacked. I even knocked off the megalomaniac criminal in his own mine ... it's now mine. *bah dum tish*

Now my contacts in the starter town want me to find the Homestead by looking for the bridge at Twin Falls ... or by finding the Smuggler's Route. The problem is that the pass I need to get there (a little north west of the Rover camp) is still blocked.

I've retraced my steps several times looking for questionable characters (the kind with a "?" over their heads) ... even killed the Warden a couple times over just because ... well ... you know ... he deserved it. But I'm not finding any new quests or discovering a way to unblock the pass. I'm stuck. I could go give ol' Damien another smack down once or twice more, but I'm not sure that is going to help anything but my bank account.

Any thoughts on what I may be missing in order for the story to progress?

Well, people in Rover camp said how to unlock small path - you need to find dynamite and blow up blockade.
Another way - explore four hills more, there are some connections after the entrance to the act 2 boss.

That isn't the barricade obstructing my path; I already opened that one to get to the mine. The one I meant was the one that has like a tank or train engine or something large that is buried under a landslide of boulders blocking the pass. Thanks. I'll investigate. I went through the door and killed quite a few more of Cronley's minions, but I don't remember if I backtracked and exited from the entrance, or if I actually took the exit you show in your map. /ponder As I was searching the area northeast of the starter town, I found the broken bridge ... and since I had nothing better to do, I decided to fix it with materials I'd collected. This area led to significantly higher level creatures than I had previously fought (i.e., lvl 35+ vs me at lvl 21-ish); they were completely killable, but I had to go slow and be careful about it. Anyway, I figured this area was reserved for another set of quests later, and I may be exploring it.out of intended sequence, so I backed out of it.

I don't understand when you say "there you enter Undercity and go through it to Broken Hills." I've explored every inch of Old Arkovia (or as much as I've had access to) and haven't run across any unexplored cave or dungeon entrances. Care to elaborate?

Wrong place, you've been to East Marsh. Refer to the map in the site I linked. Head towards Smuggler's Pass, follow Sariso's directions to get there.

Undercity is one of game's major dungeons, and one of the bigger dungeons. There is also a questgiver near that dungeon, who starts quest chain for Steps of Torment and free Skeleton Key. There is also an optional quest inside Undercity itself (you are asked to collect 3 Lore Items). So you are missing on a good portion of EXP if you skip this dungeon.

Try this map, Undercity's entrance is marked by eye-looking symbol to the west of Shrine (approx. in the middle of map).

Turned out that I must not have exited the mines using the one suggested. Thanks. Now off to Twin Falls and new adventures ... meaning ... kill more things and take their stuff.