>Brutal Rush I can 'feel' an improvement during levelling when
>just using it regardless of the situation but I want to
>quanitfy it's benefits in PK and learn when to use it and when
>not to. It has one round of lag and the effect seems to last
>roughly as long as entwine.

There's a (usually pretty small) chance each round that brutal rush will end, so it's unpredictable in that way.

>How similar is 'brutal rush' to orc 'crushing assault'? My
>guess is not at all.

Not all that similar.

>Brutal rush true or false:
>
>Reduces the number(or chance) of swings one or both opponents
>get, and penalizes further if either is wearing anything
>larger than a dagger?

Effectively, number of swings of anything but unarmed/dagger drop significantly.

>Prevents fleeing. (probably not)

I don't think prevents, but it might make it harder.

>Restricts/penalizes skills both passive and active that
>require mobility (concealed, rebound, malleability, pincer,
>impale, spin, distance and most hunter skills, etc.)

I think you can make a good argument for that, but I'm pretty sure it doesn't do these things currently. I may change this.

>Makes it harder to parry or dodge for one or both parties?

For sure yes, but I don't remember more specifically than that offhand.

That's what I can remember without digging; it's been a few years since I played a character with this skill.