ASM: How to block a user holding down F5 Key

What TPS limits have you tried? You can always put an iRule in place while you workout the ASM policy. Something to display an error message or do an HTTP::close.

when HTTP_REQUEST {

    if {[info exists refresh_count] } {

        if { [HTTP::header value "If-Modified-Since"] ne ""  } {
            incr refresh_count
        }

        if { $refresh_count > 10 } {
            HTTP::respond 200 content "Nope"
        }

    } else {
        set refresh_count 0
    }

}