Whether or not you have excellent or questionable visibility, you should always assume something unexpected might happen and proceed carefully when overtaking several cars at once.
Of course, if visibility isn’t an issue and you have a straight patch of road ahead, then sure, by all means, go to town. But even then, it would be wise to carefully “scan” each car that you’re passing, trying to anticipate if the guys behind the wheel are paying attention to the fact that they’re being overtaken and aren’t about to jump in front of you.
Then there are instances when you shouldn’t even think about overtaking, especially when you don’t have the visibility and you’re passing way too many cars as the road starts to bend.
Let’s take the guy driving this Volvo for example; he starts by overtaking the first car illegally, and refuses to slot back onto his own lane, pushing his luck as the curvature of the road starts to take away any visibility he might have had.
Sure enough, he finds himself face to face with incoming traffic and goes on to do another stupid thing, pulling off the road to his left, which is something anybody would instinctively do if they were the ones approaching him from the other direction.
It’s obvious that what he should have done was try to get as far to the right as possible, allowing the incoming car enough room to go safely off the road.
This entire incident just reeks of poor judgement.