I've never heard of a crank or cam sensor failing, so I think its pretty unusual.

There are about a hundred different things that can cause a misfire. They are one of the hardest symptoms to troubleshoot. However, you can eliminate a handful of things knowing that the problem is not specific to a single cylinder.

Start with the basics (and easy/cheap/free) stuff before you start throwing random parts at it.

I've seen problems identical to what you describe that were SIMPLE, FREE fixes- like a poor ground connection.

'97 4Runner, '06 F350, '86 4Runner, '05 WR450
http://home.4x4wire.com/erik