Can braided line be used w/ this rod? I've heard that the tip is fragile & that if the braid wraps around it, that it will snap the tip.

Just want to know how true this is, or should I just stick using mono line w/ the Crucial rod.

And if this does happen will Shimano's warranty cover it?

Braided line wrapped around the tip of any rod could break it; I really don't worry about what might happen.  

And if this does happen will Shimano's warranty cover it?

I would imagine that since your braided line would be rated at a higher test than the rod is rated for, that alone would technically void your warranty.