I am with @mpalmer here I think it’s extremely unlikely you hit real CPU limits with Discourse – I think something else is happening.
Believe me we do a lot of Discourse hosting and CPU is never the limiting factor for any of the hundreds of sites we host… CPU is important for response times, of course, but it’s rarely the bottleneck itself.
You should look at this a lot more closely before concluding CPU is the bottleneck.