Thanks for highlighting NAN. I found a simpler routing and am now planning
OSL-(HEL)-ICN-(HKG)-PER-BNE-AKL-SYD-(LAX)-SFO-(DFW)-STL-BOS-LHR-OSL
which removes the NAN issue.

I've opted for AA BOS-LHR (first time for 20 years) partly because I'm a bit fed up with BA and partly because as I am now booking with AA RTW desk (they were very professional; AY refused to do it) they require some AA metal across at least one ocean. And QF BOS-LAX because the A320 business seats look better than the AA product. Rest of the flights don't have much choice. Again, let me know if there is anything you spot!
Thanks

[edit sorry, meant A380 not 320]