I tamed a level 30 carno everything went fine until a level 30 wild Rex came in my base my carno took it on and won saving my butt. Leveling up melee damage and health as well as stamina to do this. Note: My carno had 175 melee and 1300 health.
I have a level 92 carno and it is my GO TO mount when I need to go on a hide run. The funny thing is it is not even a level 100 and yet it wrecks brontos and pretty much everything else in the general area. Try to get a carno as soon as you can because if you put in the time to level them up they are a force to be reckoned with.
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.
It is sad to see the Carno for not getting too much love these days. Whenever I try to find mutated Carno videos, it only shows a few of them before showing off Rex, Thyla, basically everything else except the Carno, and I'm disappointed. Carnos are basically a nerfed apex predator. They have the power and health you would expect while being speedy as well. They are not too difficult to tame, just a simple knock out tame. Even though a TLC could spice things up a bit, I love it for what it is.