Illogical machines?

Rating: Null/10 (14 December 2004)

Watching this movie, a question came to my mind: how come the machines of the future never have a backup plan? They only ever send one terminator at a time. Wouldn't it be more effective to send back several, so that if one fails the others can go into action? Or maybe they can coordinate in teams.
They wouldn't even have to be the most technologically sophisticated - they just have to be in large enough numbers to terminate Arnold's character. The resistance of the future would not be able to send back several "counter-terminators" so John Connor would have a greater likelihood of being killed.
I would prefer to see John Connor facing almost insurmountable odds, than to see another Terminator where Arnold goes one-on-one with the latest model only to defeat it through super-"human" will. Of course the sense of fatal danger is undermined by the fact that John Connor must exist in the future to provide the machines with a reason to kill him in the first place [I won't go into time paradox question here or my head will explode].
However, it would provide the writers with a real challenge if they have to figure out how Connor can avoid termination several times over.