Slow at processing rule?

I'd guess that the reason for the performace lower throughput of a single TCP connection is the fact that BIG-IP has to do so called late-binding in order to evaluate the rule. Again, it is not a problem in rule evaluation per-se, rather an impact of using L7 loadbalancing vs. L4 loadbalancing. Lower performance while using a L7 rule is expected, however not to the level you are seeing (order of magnitude). That makes me think there is some other factor causing the performance degradation. In order to troubleshoot the problem I'd need to see full configuration of your system, packet captures etc. The best course of action for you is to contact F5 support and let one of our network support engineers help you. It is IMHO inappropriate for this for to troubleshoot this problem.