Uh... we are the saviour of Skyrim, the Dovhakiin, who will kill DRAGONS. Mountain lions shouldn't be almost impossible to survive.
Yes, and the reason they should be killable is that we notice them in time, and avoid their blows long enough to kill them. Not because of auto-heroism.
I can imagine a huge guy in plate armour maybe surviving an attack or two, but a wizard, thief or warrior in light armour should be dead if he lets a mountain lion get in close.