I am still stumped. 
Editing the grass' LOFTs would make tall grass kind of meaningless, since the difference will only be visual.
Is the main grass in beach missions meant to be really that tall grass? Like at least 50 cm in height as it appears to be in the FPS look (making some assumptions as to the height of dogs)? Visually it doesn't look like it, and having so long grass everywhere around all the houses (where people are also expected to walk around) would make no sense at all.
Just think about it. It makes no sense for grass in those missions and locations to be taller than, say 5 cm or at most 10 cm. And such grass should not prevent dogs from attacking.
So it seems to me that a very obvious fix is to reduce LOFTs so that for example regular-looking grass or lawn areas are not actually unnatural in height.
If grass is overgrown to 5 cm or 10 cm in height, sure, it could be a bit slower to move there (1 or 2 more TU per square?) but that's it.
But if you want some areas to be really tall, there should be some logical reason for it and it should show in the visual.
On the other hand, certain fields certainly visually could have tall growth, tall enough to hamper dogs and even agents (I'm now thinking of the original X-Files movie where they run through the corn fields..). I haven't tested what LOFTs there are and whether this also affects the fields.
