lb_failed with lb mode rr does not seem to produce expeted results

[root@iris:Active] config  b virtual bar list
virtual bar {
   snat automap
   pool foo
   destination 172.28.17.33:http
   ip protocol tcp
   persist mysource
   profiles {
      http {}
      tcp {}
   }
}
[root@iris:Active] config  b profile mysource list
profile persist mysource {
   defaults from source_addr
   mode source addr
   timeout indefinite
}
[root@iris:Active] config  b pool foo list
pool foo {
   monitor all http
   members {
      10.10.70.200:http {}
      209.85.175.104:http {}
   }
}

[root@iris:Active] config  b persist show all
PERSISTENT CONNECTIONS
|     Mode source addr   Value 172.28.17.30
|        virtual 172.28.17.33:http   node 10.10.70.200:http   age 4sec


[root@iris:Active] config  curl -I http://10.10.70.200/
HTTP/1.0 404 Not Found
Server: BigIP
Connection: Keep-Alive
Content-Length: 0

[root@iris:Active] config  b rule myrule list
rule myrule {
   when HTTP_REQUEST {
        set retries 0
        set request_headers [HTTP::request]
}

when HTTP_RESPONSE {
        if {[HTTP::status] eq 404} {
                incr retries
                LB::down
                HTTP::retry $request_headers
        }
}
}

[root@iris:Active] config  b virtual bar rule myrule

[root@iris:Active] config  curl -I http://172.28.17.33/
HTTP/1.1 200 OK
Date: Sat, 08 Oct 2011 08:47:51 GMT
Expires: -1
Cache-Control: private, max-age=0
Content-Type: text/html; charset=ISO-8859-1
Server: gws
X-XSS-Protection: 1; mode=block
Transfer-Encoding: chunked

[root@iris:Active] config  b persist show all
PERSISTENT CONNECTIONS
|     Mode source addr   Value 172.28.17.30
|        virtual 172.28.17.33:http   node 209.85.175.104:http   age 4sec
[root@iris:Active] config