So when you have someone trolling but you think there's about a 30% chance you can carry, you should still surrender?
It just isn't simple by definition. When should you surrender? When the guy carrying you says it's time to surrender. He knows his limits. If you're the one trying to carry, you make the judgment call. At least that's my opinion.
I can't tell you how sickening it is when I can win any 1v3 and my team surrenders because they can lose any 4v1 (and I'm not being toxic, although tbf in a lot of these cases at least 1 of my teammates are being toxic). Just mute and let the guy who wants to carry, carry. Even if you win 2% of those games, that becomes a big difference over time. My most memorable games have been comebacks from 20min surrender votes (then 25, 30, 35, 40, 45, 50, 55 that all got denied) then we win in 1h16. Again to be fair though, that specific game no one was a jerk ;)