Refocus wasn't truly intended to be like any other action. Rather, it is a way to lessen someone's penalty for skipping his turn when he doesn't know what to do. When you have absolutely no idea of which action to take this round, instead of merely "skip my turn", choose to refocus which means you still lose your turn but at least you get some Init increase to partially compensate.
Indeed, you should never refocus unless you're the last one in the round. If you're not the last one, it's straight better to delay instead. In case you still haven't decided what to do after delaying down to last in the round, you can refocus and "appear" in the next round at higher initiative.
Note that refocusing is quite the same as delaying into the next round, and in fact it was removed by 3.5, and the delay limit was removed as well. Don't think of refocusing and delaying as specific actions, because their original meaning was to "just wait".