I have a rb450 running well. All traffic passing properly, but when I turn on webproxy my latency jumps pretty badly. ping times of 20 to 40ms are normal with it off, turn the routing to pass the traffic to the webproxy and boom I see 200 to 400ms.
Not usually, no. At the same time do you see CPU utilization increase? What is the baseline CPU utilization without the proxy running? What are you using for storage? The RB450G doesn’t have huge amounts of RAM, and NAND makes very poor proxy storage. How much traffic is flowing through the router, and being proxied?
Generally speaking without knowing those details, the built in web proxy is very rudimentary. If you need a well performing proxy run a dedicated machine. Squid works well.