Question about TAS runs

[Shikamaze]

Question about tool assisted.

Since in these runs it's possible to use RNG manipulation for some stuff, why runners don't use it for, as a example, dealing max weapon damage or having only the lowest damage roll on hits, which would always make runs faster? 

[Shepardus]

1. They do, at least in runs that have the effort put into them and that don't have too much going on to control. Here's a recent one that I like - check out the berserk punches!
2. RNG manipulation isn't absolute control over RNG - it still works the same way (which in vanilla Doom is a static table that's iterated through), so getting a different outcome in one place requires making a change in another, which isn't always desirable or possible.
3. Typically a TAS would avoid getting hit in the first place rather than try to roll for low damage upon getting hit. Also, if you're going purely for speed then taking damage isn't necessarily a problem.