[Jackaudio] DSP load

Hello I am using Jack on Windows machine. I am using the Jack to process audio in real time with few very CPU hungry VST plugins. I have a computer with 4 cores CPU but it is old machine. The playing software did not utilise the cores as it suposse to be. I have got an idea to use VST hosts, connect them and with Process Lasso to force the right core utilisation. And I have succeded the goal. All cores are utilised almost at the same level. My card is an USB interface with max buffer 4092 and ASIO driver. I have configured the Jack with maximum possible frames/buffers. With full set of VST plugins I am getting DSP load 100% what is total disater and in the same time CPU core utilisation in around 30%. Is there any way to solve that problem. Or it is just a kind of bottelneck connected with my USB interface or Jack? Regards