Hello, debg
I've also been a CoC Keeper for a few years. I mainly play 7th edition but because of the country I currently live in I've also have experience with CoC 6th edition. From my experience 7th edition is much much deadlier and investigator deaths are much more common. I feel that death is a needed part in any horror, without any risk there will be no tension(in short this is me just saying CoC 7th has alot of deaths).
For death vs insanity I feel it depends on the story used.
I see [monster strength] vs [SAN loss to meet them] are like 4:1.
Deep Ones(from Flotsam and Jetsam) [1D6+1D4]damage vs [0/1D6]SAN Loss.
Hunting Horror(Keepers Pg.299) [1D6+3D6]Damage vs [0/1D10]SAN Loss
Add to this you usually loss SAN only once per type of monster; while you could get attacked multiple times in battle. Many scenarios are made with battle with the cult or with lesser monsters in mind, or exploring the mystery and just getting a glimpse of the great old one. Any battle in CoC could lead to a death while the more Lovecrafty type of story where they encounter a truly godly being and barely ran for there life type of story could bring them to a more insane end.
I feel "Flotsam and Jetsam" is aimed for a more newer player and Keeper in mind. It brings in the very basics of Lovecraft horror; and I feel newer players are more likely to go into fights so at least being some what capable of fighting equally is better than a automatic death if attempting to fight the great old ones. I do not remember if this is stated in the PDF but if your using the scenario as a campaign then you could have them knocked unconscious rather than death. This did happen to me when I ran the game as a campaign in the first scenario. One of the player was knocked out with one hit from the monster the very first turn. Rather than instant death I told my players that the pc was knocked unconscious and it left that character with a deep cut which had her loss 1D10 APP loss and shes left with a nasty injury which is like 90cm on her back to her left arm. I've used this idea from a scenario or campaign maybe from "Flotsam and Jetsam" or it could be some other scenario which I could not recall. Many scenarios have alot of wisdom for new Keepers so we all could learn from those.