To be useful, the movements in patterns should not be reliant upon the opponent performing a sequence of actions. They should only deal with the first attack or be preemptive. From then on, the movements should give the opponent no opportunity for any choice of action. While it is true that some techniques flow naturally from one to another so that, if your opponent uses one technique, there is a good chance that the next move will be predictable. However, as the sequence gets longer, the less likely it is that the opponent's movements will flow predictably.
Some movements rely on your sixth sense to detect an attack from behind and successfully block it. When concentrating on an attacker in the front, you will not be aware of another attacker to the rear no matter how good you are. When making movements to defend against another opponent to the rear, think of the movement as a reaction to a single opponent who move around to that side.
Too many movements are against long range attacks. While it is true that practically all sparring occurs at medium or long range, most real fights are at close range. Since close range fighting is often neglected in Taekwondo training, many students look to other arts for grappling experience.