Work-stealing has been there since 1996 and is optimal if greedy. Original Cilk paper: http://supertech.csail.mit.edu/papers/cilkjpdc96.pdf

There are other techniques that are optimal like Parallel Depth First scheduling from Blelloch.

Since then there has been a lot of work for distributed work-stealing.

Boggles my mind that at "cloud-scale" people still use round robin and assume uniform workloads and that at the server level there is uniform load as well.