I'd suggest Tier 1 / Tier 2 discussion will have a longer term detrimental impact on the RAN than anything short of killing DDG/FFG numbers. Arguably it is what got us into this mess in the first place. Someone here (and I have to run sorry, so can't find them - but
@Volkodav?
@ADMk2?) has put out a logic chain (that I agree with) that shows how the ANZACs were the Tier 2 combatants to the CFA/OHP fleet that, in order to save money, we simply treated as 'generic major platform' when it cam time to replace the DDGs. Meaning they now form the bulk of our fleet, and despite upgrades the what could have been paths are better.
I also think that while some here argue that corvette = Armidale replacement/addition, the DSR is not phrased that way. It could be read that way, but it also could be read that we will sacrifice major platforms for them. I wear many hats, under every single one that's almost criminal. We don't have enough FFG/DDG now, we don't have enough come 2040. And yes, I have actually put forward plans (including cutting my own budgets) to boost FFG/DDG numbers.
The reality is that Australia is a maritime nation, who's maritime AO reaches from the Suez to Hawaii, from Antarctica to Japan. There are huge parts of that where small ships cannot go because of their small bunkerage. The weather adds even more negatives. I know there are actual sailors on here (and noting I have spent more nights on board HMAS Brisbane II than an amphib speaks to my Army-ness) but having worked closely with a minehunter LCDR for two years, their stories of steaming around that AO borders on horrifying. Finally, I know there are people who have an unnatural fascination with VLS numbers, but every FFG/DDG has more magazine depth than a small ship. So....the point is?
Finally, I see DDG/FFG like the CL/CA of 1936. While big and expensive, they were absolutely needed. Can you imagine a DD taking the damage of HMAS Australia? Or fighting some of the actions of HMAS Sydney? The redundancy, the range, the overall capability - all were essential to our fleet's operations. If you want, corvettes are the emergency program of O- to Ca-class destroyers. Built rapidly and quickly, but meld with the proven, cornerstone capability of the DDG/FFG.
TL/DR: Tier 1/2 is okish for short term, detrimental for long term. DSR isn't clear. Corvettes are not feasible replacements for DDG/FFG. We need more of the latter.