The timing of your visit is everything when going to Deal's Gap. If you are going to ride it, visit on a Tuesday or Wednesday. I've done both and literally been the only person on the road the entire length and back. If you want to see people and bikes, go on a weekend, particularly Saturday. I've seen it so packed it was hard to get your bike in the parking lot.
I seem to recall there is only one spot where there is no a double yellow(?). Given how tight it is in many places, any passing is risky, even when the person in front is cooperating. My view is that for many riders, Deal's Gap may be the most technical road they have ever been on. If I am "stuck" behind someone, I don't assume they know I am there because they may be so focused on the road ahead that they are failing to watch behind them. At the pace some riders want to run though, even if slow riders are watching their mirrors some, a fast rider may not wait for them to notice or give a chance to move over. I had this happen to me and the fast guy passed me on the inside without me knowing he was coming. To say that this made me angry would be a gross understatement. I would be more than happy to move over where possible.
For the really good riding though, I prefer to avoid Deal's Gap. There are many roads in the area that are as good or better and have almost no traffic, even on weekends.