Here's how I updated to 4.4.4. This applies to anyone using Windows. I was on stock 4.4.3 with Xposed, ElementalX kernel and rooted via SuperSU. This will not wipe your data and, if you use Xposed, all of your settings for your modules will be preserved.
Make sure you have done the following before you update using the factory image:
1. Uninstall Xposed Framework but don't uninstall your modules.
2. Choose the Full Unroot option in the SuperSU app.
3. It might also be a good idea to flash the stock kernel if you're using a custom kernel. You can find the stock kernels for 4.4, 4.4.1, 4.4.2 and 4.4.3 here. Use the one for 4.4.3 and flash it in recovery.
After doing these steps, reboot into the bootloader. On Windows, extract the factory image folder named "hammerhead-ktu84p" which contains:
Open the file named "flash-all.bat" in a file editor in Windows, I prefer Notepad++. Look for the line,
fastboot -w update image-hammerhead-ktu84p.zip
That worked for me, thanks. I wasn't quite sure how to update from 4.4.2 to 4.4.4 but this guide worked. No data lost. After I did it I saw the comments about removing userdata.img and recovery.img but no big deal, just meant a few times going to bootloader to flash TWRP and SuperSU. The only step I didn't do was choosing Unroot in SuperSU, I forgot to be honest, but your method still worked without doing that.