I think part of the problem with your argument is that a lot of the issues you're bringing up with torture are really just issues with interrogation in general. Suspects are perfectly capable of lying or giving out bad information during a humane interrogation. False confessions happen all the time even without torture being a factor. You would still need to verify any information a suspect provided under humane interrogation, and so on.
Then again, that might be the best indictment one can level against torture. If it has all the same problems as normal interrogation methods, then that suggests that in most cases any possible increase in effectiveness is minimal at best. And that's not enough to justify doing something morally abhorrent.
Fortunately in a world with magic there are even better ways to get information out of someone which theoretically always produce true information. They would not even need the psychological manipulation of modern interrogation methods. The best magical solution would probably just be to charm or dominate someone and then ask them. Paired with modify memory they won't even know they had been interrogated.
"Lawful Good is the best alignment because it combined honor with compassion. Also if someone gets in your way and they are wrong, you can torture or beat them until they give into your demands."
I have always had the above mentioned method of dominate/ask be the LG enhanced interrogation technique of choice. It is humane, quick, effective and does not violate anyone's alignment based codes of conduct. The only drawback is that it requires a relatively high level spellcaster, but in an emergency charm person would probably work pretty well too.