I sat and watched a Drake and a Paracer fight in the swamps just now, and the Drake took 0 Damage at all from the Paracer. Despite the Paracer doing it's thing and trying to stomp on the Drake several times. Not a single value of HP was lost.

I'm not sure why this occured, but admittingly it's a little upsetting that things can't seem to do much if any dmg in a wild setting to these creatures. And while mounted on a tamed creature, the only things that appear to aggro are T-Rex (and perhaps Giga) when you're near them.
Argents won't aggro, raptor, Carno.. Unless you pick a fight, or another beast from your mod there is nothing trying to kill you while mounted on one of your creatures.

I get this is a "Tame a whelp off Rex Kibble (rather than a quetzal) type end-game scenerio" but it's a little upsetting it's so far on the "end-game" scale that nothing is even trying to be threatening.
While out on my Drake I'm more worried about getting too close to Kapro than I am flying/walking around heards of Carno/Raptor/Argents, etc;
This also makes it so they have no real natural preditors themselves, like the Giga.. Unless it's a Giga maybe.. Which is also kind of frustrating to be honest. Sure they're "Rex Level" or even in some cases "Giga Level" if you consider HellKites but even Rex can die off to a Paracer or Bronto.. A Drake seems unable to even be hit