I have heard a number of people complain that very hard isn't realistic because you can shoot an enemy in the head a few times before they die. This is true, and it's also not very realistic for the Courier to be able to survive many shots to the head, as is the case with normal mode and hard mode. (and in the opening cutscene of the game, for that matter

Unfortunately, on normal mode and hard mode, the game is simply too easy.
In my case, Enjoyability and Balance trump Realism. It's boring if I'm walking around practically in God mode and there are no challenging combat encounters. This was the problem with FO3 after having played it quite a lot. I like the feeling of finally making it through a tough fight where I had to die a few times before figuring out the best strategy to approach the enemy.
Even on very hard mode, combat in FNV still becomes a bit too easy if you have the super slam perk, for example. But in any case it's a lot more balanced (read "more fun") than FO3, especially with hardcoe mode + harder hardcoe rates mod + expensive wasteland mod.
Also, if you want to experience challenging combat once in a while, I believe this is not possible while traveling with companions.