I was a MT warrior from Kunark all the way through DoN (or slightly after that, can't quite remember), and can attest firsthand that your statement is absolutely untrue. Every guild I was in had Pal/SK in the tanking rotation, and depending on the boss, their snap aggro was a huge bonus as it allowed the raid to engage earlier.
Some bosses hit so hard that defensive was a good thing, yes, but the majority weren't in that category. For those that did hit that hard, defensive wasn't the only reason that warriors shined: AC and mitigation were better for us. But it wasn't often that this was an absolute requirement.