Agreed, Sanity rolls are game killers.
It is a mechanic of Russian roulette with 5 bullets in a 6 chamber revolver
If you want to instill the fear of the event then I would recommend a chart of horror effects, such as:
hair turns completely hair
hair falls out
temporarily deaf or blind or dumb or other or all
partial paralysis
mini stroke
normal speech is replaced with an arcane language
age 10-50yrs
stunned
KOed
see other characters as evil frogmen or zombies or "insert your favorite"
etc.
And continue rolling on the chart as you see fit...
If players are in the presence of an Elder God or the like then each round they save vs magic for example and if fail then they get a chart result...10-25% should be thrown up or poop on one's self...
“The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents. We live on a placid island of ignorance in the midst of black seas of the infinity, and it was not meant that we should voyage far.”
― H.P. Lovecraft