Tanks in my roulette runs seem to be hitting some pretty big extremes on how much preparation they actually want when I'm running. I've seen numerous that start rushing forward without waiting for Protect (let alone any other mitigation), and never once give time for anything in between pulls. The best I can hope for is a Swiftcast-Stoneskin II between pulls. The other seem to match the original poster's description of shaking in their boots until they have every ounce of prevention possible. These days, the former is more common.
My opinion? I'll cast it if I know you need it. You don't need it if we only have three measly enemies ahead before a brick wall. You could use it if we have a potential huge pull ahead, or high hitting magic damage mobs.