the bloodiest battle

I'd say the Torvosaurus pack would win.

My vote's on the Torvo pack. 

Torvosaurus for me!

What if I threw in a rex 

Then my vote would be Rex. Don't though, you already threw choices out there, and it gets difficult writing these fights with multiple competitors. 

I know it does and it is a story fight and the herbivores are in herds

I'd leave Rex out at this point. You've got enough competitors as it is, and the last thing you need is more. Looking forward to it.

Torvo definately seems to have an advantage. Diplodocus might be able to defend itself if the predators kill eacother...