There are several other reasons I don't like to ride like that:
1. Since its not a motocross track that you can assume there aren't any big rocks or trees fallen into the path, you have to be able to make split decisions to get out of the way of obsticles and would rather do that without forcing the other guy off the road.
2. Blind corners, I mean I can't tell how many times I come around the bend only to be greeted by a truck comming full speed had we been going in tandem one of us would be road kill. Hell, its hard enough to get out of the way of some of those guys even when you're not tandem!
3. Cliffs, a lot of the logging roads are on the edge of a cliff, would rather not ride next to the edge of the road which has already had landslides and been washed out partially with a 1000 foot drop!
I guess part of what made it more awkward for you is that I forgot to initiate you into the Official Tandem Road Riding Safety System (OTRRSS). This is how the system handles each of your three problem areas.
1) When encountering an obstacle that requires a lane change, the rider with the clear lane (if any) should continue at speed, while the rider encountering the obstacle should slow to let the other rider pass, before coming in behind to take the clear lane. After the obstacle is cleared, the rider who switched lanes can then catch up to the other rider and resume normal riding.
2) There is a hierarchy among the two riders in formation, a "flight lead" and "wingman." Preferably, the flight lead should be in the right-hand lane, but this is not universally adhered-to. When encountering a blind corner, the flight lead should pull roughly two bike-lengths ahead of the wingman, allowing him to see through the corner in advance. If another vehicle is oncoming, whoever is in the left lane should get into the right, or even to the right shoulder, and both riders slow down considerably for the pass. If the wingman is in the left lane, the flight lead makes a gesture with his arm, signalling for the wingman to get the hell out of the left lane. If no vehicle is encountered, once both riders can see that the next straight is safe, they resume riding line-abreast as normal.
3) In any situation where you feel the road is too narrow, too rough, too inconsistent, or too downright hair-raising for tandem riding, just fall back and transition to riding single-file. The #1 rule of riding is to never do anything you aren't comfortable with from a safety standpoint.
So as you can see, we have thought this through a decent amount, even if sometimes the actual event doesn't work out as elegantly as it does on paper (bikes with different amounts of power really complicate things a lot, as you can tell in the video.)