If there were two timelines what is Dolores doing in the MIB-timeline? We only see her 30 years ago, don't we?
No. The two timeline theory has Dolores retracing her steps from 30 years ago in the present. That's why they have the shot in the railway car where she's standing with William and El Lazo and the camera moves and you see she is all alone in the car.
Here's a very helpful timeline explaining the William in Black theory (with some extra theorizing), shamelessly stolen from Duckroll at the Neogaf forum:
- MiB says he has been coming to the park for 30 years
- The last critical failure was mentioned to be 30 years ago
- Arnold died 34 years ago
If we put everything together it would possibly look like this:
37 years ago - Ford and Arnold start Westworld together and they spend 3 years building the park and perfecting the tech
34 years ago - Arnold kills himself through some elaborate scheme and leaves hidden code behind with Dolores as a trigger to destroy the park
30 years ago - William and Logan visit the park as Delos executives looking to buyout the park which has been running for several years but running low on funding now
30 years ago - Arnold's code in Dolores activates for the first time leading her to William and Logan, and leading her to "the maze" which is Arnold's grand plan
30 years ago - William stops Dolores and saves the park when things go completely south, Delos buys it out
Today - William has been drawn back to the park again and again over the years looking for meaning behind what happened 30 years ago, while Arnold's code activates in Dolores again, things are coming full circle