Must have for PvP. I play single player, and was out hunting on my new spino. I attacked one and it spun me off my spino. Therefore, lure poeple to water and knock them off any mount. Haven't tested with my Rex or brontos yet, and won't.
Baryonyx are quick like Allosaurus and do just as much damage (but don't get a pack bonus). They don't use oxygen for swimming and can sprint in the water. Right click in the water does an AoE stun that lasts about 10 sec. Their 'C' is a... Taunt? They also jump and you can fire a weapon from their back.
It's like a small Allo combined with a Kapro, in my opinion. Useful on both land & in the water. Use its secondary attack while swimming to stun, attack, and harvest. Does NOT stun Cnidarias, though, so do not expect to overpower them.