So... The answer is kind of simple. Adrenaline doesn't make you superhuman. It does increase athletic ability a little bit if adrenaline hit you the right way, but it likely will not. Even if it hits you the right way, it is only a bit increase usually and you will still get over powered. The adrenaline also helps you focus and amplifies your senses, but in a kind of tunnel vision focus so that you stop paying attention to things outside of your focus. Which can lead to you being blind sided by another attacker. Your ability to think clearly also goes out the window, which makes you easier to panic and resort to doing something stupid over and over when it does not work. And your fine motor function goes out the window too, so in the worst case you might struggle to work a door knob or use the touch screen phone to call 911. That and your ability to measure and experience time correctly is altered too, and so much more.
Essentially, if adrenaline hits the correct way it might help a little, but more often then not adrenaline is much more of a burden than a help. It's much more predictable and easier to fight in a calm mindset without the adrenaline alteration.
As to how do you fight without pain? Well I categories techniques into two categories, pain compliant and stopping powered(the exact term doesn't really matter btw). Pain complaint techniques are the techniques that just deals pain and saps away at the other person's will to continue fighting. I really do not like these techniques because more you need them to work less reliable they will be. For example, if I'm playing around pain compliant technique will show great results, but if the opponent and I am fighting for our lives then no amount of pain compliant technique will sap the other guy's will to fight. More serious the fight less effective these are.
The stopping powered techniques are the techniques that physically shuts down the opponents ability to continue fighting. A KO is a physical condition that shuts the opponent's brain off involuntarily. The opponent doesn't get a say in the matter. Same goes with snapping something with a joint lock. Also with losing consciousness from blood chokes. Oh, and losing consciousness from blood loss through external or internal damage, though this is more from weapons than empty hands.
Essentially I rely on stopping powered techniques, and I can take out a person whether they can feel pain or not. For me it doesn't make any difference. Any martial artists worth their salt will also have plenty of stopping powered techniques at their disposal, so they should be able to handle people that can't feel pain just as well.
P.S. Just re-read the question and I just wanted to point out adrenaline does nothing for endurance at all. So technically even if you were super human I could just wear you out before turn your brain off.