Staggered riding is great, especially where the roads are wide and good, but it is common practice to "break ranks and ride single file, even here in UK and in Europe, when the road narrows or doesn't lend itself to staggered formation. When doing this though, it is important to extend your distance from the rider in front to allow that extra safety zone for stopping in a hurry.
We are lucky not to have too many deer here, but we have more than our fair share of car drivers who are happy to act like them and surprise you when least expected. Actually you might wish to argue that last comment, since the deer are doing a fast brain job of working out fight or flight, the humans are mostly brain dead and just going about their business on autopilot, whilst concentrating on braking the law, by talking on the phone or thinking about something other than what they are doing with the dangerous weapon in their hands!!!!!
Lane changers are another one to watch out for, especially the many foreign lorry drivers that frequent our roads, with left hand drive vehicles, they often cannot see us as we are passing them and pull out suddenly. I have had this happen on more than one occasion and even when driving a big van. Twice that I can remember,I have smoked the tyres in an effort to avoid the inevitable.