Just watched the film. Zemo was phenomenal, by far the best Cap villain in my honest opinion. If there's any complaint I have it's the fact that his design is non-existent, but really with how good he was portrayed, I'd say it barely matters unless you want him represented in your collection.
As for Crossbones, I'm not really surprised with how he was handled. Short as it was, he served his role well, and for the general cool factor I thought he was fine.
Aside from Ultron wrecking Sokovia which serves as the basis for the Accords, Crossbones actually ends up being a key player in an incident at the start of the film which causes the registration to be pushed forward even more for the heroes to sign on. He actually gets two great fight/chase scenes with Natasha and Steve until he ends up trying to kill himself with Steve by blowing himself up with a bomb vest. Wanda manages to intervene and contain the blast which saves Steve, but she couldn't control it well enough which results in the explosion killing a lot of civilians. This incident basically sets up the film while using what Ultron did in Sokovia as the main backdrop of the cause for the Accords. At the same time, Wanda screwing up ends up haunting her for most of the film, so it's not like he didn't leave any impact at all. For all intents and purposes, he has a very similar role to Nitro in the Civil War comic.
So yeah it might have been a small role, but it's a pretty hefty one that helps to push forward the main plot of the film. My only gripe with this figure is how the film depicted him as having extra gear (a fancy gas mask that goes over his existing helmet and he actually used firearms) which would have been nice to get since it seemed to imply that it was standard gear for him. The figure basically depicts him without all that extra stuff and it's meant to represent his melee combat "mode" of sorts when he's shed all the tactical gear off for a fist fight.