I'm keeping my vote of "no crit, no spread, no intel crit", because I don't think it's necessary to have any of it on and I like the feeling of consistency. But I'm not going to argue against any claims that crits and spread are okay. I really don't care whether they're on or off, because it all matters so little in the big picture.
If you're killed by a crocket instead of placing that final killing shot on the soldier who fired it - who's to say you definitely would have killed him? A lot of other (semi) random things could occur, such as a third player joining the fight. Or you could be mistaken in your estimation about your shot being a killing one. Unless you're a highly skilled competitive player who can count damage and estimate the enemy's remaining health, and on top of that you have good enough aim that you're sure you can hit - unless that is the case, battles in TF2 aren't going to be predictable and stable just because crits and damage spread is off. And hey, in the end it might not matter if you get killed in that one battle or not. What if you're killed by a Heavy around the corner 2 seconds later anyway?