Ahh, this reminds me of some species of animals which only come together to raise their young, and then split up again when the offspring have grown up and gone on their way.
According to the BBC Series walking with dinosaurs T-Rex didn't even wait till that. It was just mating and then Daddy was gone again. Sauropods are not supposed to have hatched their eggs either but more or less left them to themselves. Pterosaurs... well, let's not get into that. I'm not sure about Stegosaurs, but from the scientific point of view the only one to have a good chance of some kind of two parent family life would be Ducky.
I think the most sharpteeth we've ever seen at one time is...3?

In LBT 10. But they didn't make a herd either, but ran into each other by coincidence (as was the case with the two sharpteeth in LBT 6).
I suppose this could be because the writers couldn't think of a good story on how the LBT characters could plausibly defeat a very large group of sharpteeth.
Perhaps the writers realize that there is not some kind of "war" going on between sharpteeth and leafeaters. They are not out to kill each other for hatred, but for "the circle of life" so to speak.
A larger flock of sharpteeth would need a larger amount of prey to support themselves. They would have to kill more and before long a herd of sharpteeth would probably empty a hunting ground which would have supported a single or a few sharpteeth for a long time. Moreover I suppose their aggressive nature is working against any plans of the big sharpteeth to team up in large herds. The problem is not the same for the smaller raptors who don't need as much prey as the larger carnivores.
It would not make any sense, it would even be harmfull for the large sharpteeth to team up in large groups.
Actually we see a whole pack of Raptors in LBT 5, they're like 4 or 5.
In the opening scenes?
There were four in LBT 3 too (one of whom was knocked out relatively early so we saw just three for most of the time).