Without having to trawl through the CX website and get the calculator out, can anyone tell me if CX Diamond requires a similar level of travel to attain as QF Platinum?

Without having to trawl through the CX website and get the calculator out, can anyone tell me if CX Diamond requires a similar level of travel to attain as QF Platinum? Also with all the talk of QF reducing status credit/points earning with CX flights, among others, does CX have a lower earn rate for their equivalent of status credits on QF flights?

It's much harder on CX. Diamond status requires 120,000 miles or 80 segments (J class earns at 125% of miles flown or 1.25 segments). Further if you are starting "cold" CX resets the tier counter at each tier level - so to go from nothing to Diamond you need 30k+60k+120k = 210k miles. On the upside CX doesn't discriminate between OW partners for earn purposes.

I earned QF PLAT with 1 J/F round trip AKL-SYDNEY-HKG-LHR plus 1 round trip J AKL-SYD-HKG. That would have just gotten me Silver/OW Ruby on CX.

Its actually good that Australian FF's are finding out what a lot of us have known all along - even with the Qantas FF changes they still amount to a great value scheme for FF's.  I am a member of EK and SQ and I have to say QF is head and shoulders above both particularly in terms of status and that points don't expire (as long as you have one active entry every three years).