irule-not-matching-uri-as-expected

Is the use of regexp necessary in this case? I was told to avoid regexp whenever possible since they are rather CPU intensive. In this case I think you could just use starts_with instead:

{[HTTP::uri] starts_with "/data/main.js?id=100&"}

Of other notice is that you're using req_count as a global variable, which is really bad for performance since it will demote the virtual server associated with this iRule to a single CPU core. That whole thing is to limit the number of requests to siteA_http_pool, right? I think there would be more efficient ways to do that. Let me think on that.