It could be a flash thing. To narrow it down, try Netflix in Google Chrome which has a reliable version of flash built into the browser.
Well, Netflix uses Silverlight still, though youtube uses the built in flash in ie11. Do try firefox or chrome. That said, both are pretty hard on the hardware, do you have the tablet in a case? Is it running hotter than it does in VLC. When does it crash, when you attempt to load the video or a couple minutes into it.
I had a issue on my laptop with youtube that it crashed every time it finished playing a video. I just uninstalled and reinstalled Adobe Flash. While this may not work for you, wouldn't hurt to do that for flash and Silverlight, maybe reinstall the video drivers while you're at it.