Dual spec came at the same time as Ulduar.

Introduced in patch 3.1.0, dual talent specialization is the ability to switch between two talent specs, glyph sets, and action bars on each level 40 character.

I have a feeling he meant having two sets of gear to fill two roles rather than the actual, in-game feature.

Before patch 3.1, "Dual Spec" was having both dps and tank (or healing) gear, carrying around stacks of glyphs and having to visit your class trainer multiple times per week. It cost hundreds of gold, pissed you off if you made a mistake in your talent build, and was overall just a pain in the ass. Dual spec should have existed at least since the start of Wrath, if not even earlier. Pure classes might not care about whether or not they had a second build available, but for some raiders, the feature has saved literally tens, if not hundreds, of thousands of gold.

@Randomize:

"Dual spec should have existed at least since the start of Wrath, if not even earlier."

It was technically slated to drop with 3.3 and/or Wrath launch, IIRC. I know I had a couple of Kara two-handers banked at the end of TBC for Titan's Grip awesomeness as soon as dual spec went live. But as the months dragged on and I leveled to 80, it became increasingly clear that we weren't going to be getting our dual specs anytime soon, and I got to the point where I had to vendor them to free up space, as the quest rewards and crafted items I had access to were already better.