Same old story, bought to do one job then forced by government procurement decisions to do another. They were designed and built to be patrol frigates supporting a force of six to eight high end general purpose guided missile frigates / destroyers but were forced to step up and fill the shoes of these high end general purpose vessels when successive government failed to order proper replacements.
The first plan was the ANZAC WIP (Warfighting Improvement Program) where it was inteneded to fit AEGIS and SPY-1F to the ANZACs, I am not sure how much was wasted on this before it was realised that it wouldn't fit and would stuff stability. ASMD is the second attempt and appears to be a much more suitable system the trouble is the platform is still over loaded hence the significant reduction in speed. When I look at an ANZAC I can't help but wonder how much better off we would be if they had been followed by a stretched FFG version, with a larger VLS and greater stability margins, to replace the DDGs and FFGs; imagine these larger, more capable ships fitted with ASMD instead of the ANZACs, they would give the AWDs a run for their money, capability wise, while being far more affordable and permitting the RAN to have maintained hull numbers.