I have a 168 Carno that's a literal beast, it goes against practically everything I throw against it, kills Low level Brontos EASILY, and that's with a mere 150% Attack, I use it as an overall mount that is helpful as a guard dog. Take one and have fun! :)
Tamed carnos are excellent almost all around: their health, attack speed, and base damage allow you to take on most of the creatures on the island, including Rexes and Alpha Raptors. Having a mated pair greatly strengthens this quality. They run fairly fast and can carry a lot, making great transport mounts. They are a fairly good harvester of meat and prime meat.
Their only real disadvantage is a slow stamina regen, even when stood completely still.