You can create a rule on Proxifier to exclude an application from the proxy (by setting the ip to 127.0.0.1, which means localhost). But I'm not sure if you can single out runelite as an application, because I think the process is called Java when it's running, so excluding "Java" would defeat the purpose, since that would exclude the mirror stuff too. So I think the workaround you're doing is your best option. That being said, if you want to regularly play your main whilst botting, you could set up a VM and bot inside of that.