If you're talking about the Defense action being useless in Super Mario RPG, then yeah, pretty much. I rarely used it. It does cut damage on you in half, and combined with the timed defense, can cut damage on you to a quarter I think. That's pretty useful in matches where you'd otherwise be killed in one or two turns. But more often than not, my allies could take a beating and still keep on ticking, so it was just better to attack.
If you talking about timed defense... well, Toad taught you how to do that at the start of the game. I forget if he said anything about the timings being slightly different. Used to bug me at first because an enemy quickly races up to you and waits a second before attacking, throwing off your accuracy. But that's part of the fun y'know. Timed defense is the only way (that I remember) to avoid instant-kill attacks if you don't have the Safety Ring (although it sets your HP to 1). ...Man, that Safety Ring was awesome. And it's immensely satisfying to do a timed defense against that one boss in Monstro Town who has invisible attacks.