Completely normal, why would a process use anything less than all available resources? For a demanding process - you should be questioning why it is not using more than 60% - you would hope for it to take advantage of 100% of that core, not just 60% - so you could be limited by disk IO, memory bottlenecks, kernel optimisations etc.
Bear in mind, PHP isn’t thread safe, so the most it could use is 100% of a core, not 100% of 2 cores (or as you put it 200% of 400%).
I’ve attached the a load average plot from one of our servers running 8 (busy) stores.
Having a dedicated server doesn’t mean anything to be honest - its knowing how to take advantage of it that makes the difference. If you want some professional advice on set up, feel free to get in touch
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