DuetHeuristic-BM and nsurlsessiond hogging CPU and Memory on MacBook Air
This link

https://discussions.apple.com/thread/7810604

explains that nsurlsessiond manages network connections and DuetHeuristic-BM is a service that is used by Spotlight when indexing. Perhaps the DuetHeuristic is stuck on a file on your computer and is stuck in an endless loop.