I have used 30# fireline for pike and have had bite-offs - and these were not large fish. Also tried 30# flourocarbon and had the same experience (two in one morning before I switched). I keep defaulting to wire, even in bass/pike situations where I'd really rather leave the wire at home.
Years ago I got some heavy kevlar tippet material, which, unfortunately, I can't seem to find anymore. It works great for pike - have not had a bite-off yet but it will fray over time....TIM