As far as the Tenontosaur and D.antirrhopus site, the Tenontosaur was a juvenile of course. A D.antirrhopus hunting party of about five individuals couldn't take out a healthy adult Tenontosaur, they could only take out the weak, sick and young, as many group hunters today do. D.antirrhopus wasn't always successful in its kills as seen at the Tenontosaur and D.antirrhopus site, at least four individuals died in the attack
Not all theories are able to be tested, it is a theory that T.rex was a scavenger but there is no way of testing that. (But that's a post for another time.)
If you look at the evidence of other Tenontosaur sites, the amount of teeth is amazing. The teeth alone should be some sort of evidence that at least D.antirrhopus was a pack hunter.
(p.s.-Dromeosaurid behavior is something I've always been interested in since seeing Jurassic Park for the first time.)