I used a 135mm on a FF body (slightly longer than the 85 on a crop) and found it very useful but I wasn't shooting quite the same kind of stuff you are...
Still, considering your other choice goes up to 70mm, there is not much difference and you gain speed. And what Derrel has to say about this lens definitely confirms my choice. But, that's just me.
This entire "area" of lens focal lengths and camera formats is an area I'm very,very familiar with. It's kind of one of my areas of interest. The thing is, with an 85mm lens on FF at 20 feet, you get about the same field of view as you do at 34 feet on a 1.6x Canon body, and just slightly shorter on a 1.5x camera. The difference between 20 feet and 34 feet means the difference between being able to actually MAKE a full-length head to toe portrait with a full frame camera using your 85mm lens indoors in a "normal room ", and being forced to stand literally 34 feet away if you have a crop-body camera.
The loss of angle of view, 1.5x or 1.6x, is a potential advantage when you need to shoot with a 300mm lens across a soccer or football field. But that same narrowing-down of the lens' angle of view in social/news/close-range shooting means that DX-format bodies can often times make it really tough to get the wider-angle shots some people want, and the 1.5x to 1.6x field of view narrowing on telephotos makes your 85,105,and 135 lenses simply too danged narrow-angle to actually "use" in many locations like patios, decks, living rooms, smaller camera rooms, and so on.
The traditional focal lengths like 24,28,35,50,85,100,135,200,300 all were designed for FX format cameras.
It might not seem like the difference between an FX and DX format camera makes much of a difference, but it really,really does when it comes to prime lenses and how you actually can use them in the real world. And the same with a lot of the older zoom lengths. If you have unlimited space to shoot in, DX bodies are great. Indoors, the DX format imposes its 1.5 to 1.6x penalty on all your lenses. Sometimes that's okay,other times it's not okay.