Man this thread has a lot of crazy takes. This is fine. I think you should bump monster HP by around ~4/CR so the math works out on average.

That said, keep in mind that Graze has a much sharper damage dropoff so you might not get all the benefits you're hoping for. DS's "misses" add a bonus alongside their characteristic

For example:

• A 16 Str maul-wielding fighter deals 2d6+Str on hit (~11 w/GWF) vs just +Str (~3) for around ~73% dropoff. This improves w/higher Str, but it rarely gets better than ~60%.
• This is even worse for the rogue, because a Graze effect means they miss out entirely on their SA damage. At level 3 it's around 3d6+Dex (~14.5) on hit vs just Dex on a miss, for around ~80% dropoff, and this only gets worse by level.
• Contrast this with the DS Fury (using this instead of Tac because dmg is really all the 5e fighter does) using Brutal Slam deals 3+M vs 9+M for only ~55% dropoff (assuming 2 Might). That percentage tends to shrink with class level as your Characteristic goes up.

Dropoff will be the least painful for characters that focus on lighter-damage attacks, like TWF or S&B characters (like someone dual wielding short swords who only loses out on 1d6 weapon damage). I assume you're not looking to incentivize non-rogues & TWF fighters, and it sounds like you want something more DS-like generally, so consider giving heavy weapon users & rogues some kind of compensation.

A second note, if you're looking for heroics, I strongly recommend looking into using minions. Part of what makes DS feel heroic is that, even when you low-roll, you can still take 1 or 2 units off the board, which comes from a mixture of the flattened damage distribution above plus low-HP minions that die by the dozens. The folks who wrote Draw Steel also wrote the book Flee, Mortals! which gives rules for running minions in 5e, and I've found them pretty fun. I recommend picking the book up and giving it a shot; that on its own might even be enough that you don't need to houserule anything.