I think Urthstripe was silly when he jumped of Salamandastron because he could have easily defeated Ferahgo by himself without dying. So...did Urthstripe waste his life?
Listening to the audiobook right now, and honestly? Kind of. I feel like he sealed his fate the moment he agreed to fight Ferahgo and Klitch. He was so suspicious of vermin towards the beginning of the book, so I don't know why he believed they would fight fair. My only guess as to what happened what he'd given up hope and rather than admit it, he chose to go down swinging.