I'm confused. Can Waboku stop one of your monsters from dying?

Or does it only save you from losing life points? I've heard that the former is true.

Waboku prevents your monsters from being destroyed in battle as well as protect your life points.

The analogy I've always used with Waboku is this. Let's pretend your Gemini Elf and my Archfiend Soldier decide to do battle. We both have an ATK rating of 1900, which means your monster is going to have to get hit with 1900 units of damage in order to be destroyed.

We each get to take a swing at each other. Archfiend Soldier goes first and wacks Gemini Elf. Since soldier hits with a force of 1900 units, it meets the requirement and Gemini Elf is destroyed.

Now Gemini Elf gets ready to swing, but being the fiendish sort that I am, I have this handy little waboku sitting by that grabs your sword from your hand right as you take a swing at Archfiend Soldier. What's the result? 0 units of damage is inflicted upon Archfiend Soldier.

Now we compare stats, Gemini Elf had enough units inflicted upon itself so that it is destroyed. But Archfiend Soldier didn't have any, there's no battle damage inflicted as a result or anything like that, Soldier is simply not destroyed.

While verbose, hopefully it helps explain how the card works. Where things really get interesting is when you replace my Archfiend Soldier with say a Kozaky or something with a smaller ATK value.

Hope this helps.