Very effective as a battle mount/travelling companion. I mostly play on single player so an effective companion is vital. I tamed my Kopiona when she was level 32...she's at 62 now with 200% melee damage, over 800 health and quite a few surprising kills notched into her tail.
Some noteworthy accomplishments (without my assistance) are:
-1 Carno killed (lvl 30)
-1 Spino (lvls 3)
-1 pack of 4 Raptors (lvls 36, 24, 18, and 50)
-Survived a Rex attack (lvl 24) after I had died with minimal health loss.
Coupled with its torpor inducing attacks, it's also great as a taming mount.
In my opinion, these guys are the best, go on, say i am weird.
First, they are very easy to tame, all you need is a few spoiled meats and a bola, tranq arrows or even slingshots will do.
Second, after they are tamed, they are super useful, you can use them for cheap creature knock-outs, plus, if you tamed one in a cave, then use it for exploration, nothing in the cave can pick on you, making it easy to get to the artifacts.
Third, they are super easy to care for, they eat spoiled meat as well, so if a stack of meat spoils in its inventory, it will still eat them.
They have decent speed, stamina and melee damage, and can cross over tough terrain that most dinosaurs can’t.