Aaron,
b verify load actually does not verify syntax of rules on BIG-IP 4.x. Try following simple experiment (to be executed in BIG-IP v4 CLI, a.k.a. bash shell ;-)):
cat < test_file
rule invalid {
this is not a valid rule
}
EOF
b verify load test_file
See the output from
b verify load test_file?
If you did
b load test_file, you'd get syntax error (and all of your running configuration would have been nuked).
The sad truth is that there is no way how to verify validity of an iRule before attempting to load the configuration in v 4.x.