In any case the RN had dozens of Destroyers and Frigates which were organised in 1963 into 8 Destroyer and 7 Frigate squadrons, each of these had a similar number of escorts as the entire RAN could put to sea in the 60s. This comparatively huge number of escorts required command at sea, hence the RN needed cruisers and DLGs with command facilities.
The RAN in practice slotted it's two deployed/stationed escorts into these squadrons when in the FESR and commanded independent Task Group/Elements from the Melbourne when 'surging' for annual FESR/SEATO exercises. If required to operate independently the Melbourne would still command ~4 RAN escorts as part of it's Task Group and any escorts left over to form a Task Element wouldn't be big enough to require a ship with command facilities.
The planned RN combat fleet heading to the 60s was four carriers, five cruisers, forty-seven destroyers and frigates and thirty submarines.
The number of escort cruisers initially required was eight, one to escort each carrier and four to provide two for independent operations. This dropped to six, once the decision had been made to get out of the conventional carrier game, and eventually dropped to the three Invincibles finally built.
There were meant to be ten Counties, four were deferred to permit the construction of the initial escort cruisers, with two of the four eventually being built later. The Tiger helicopter conversions were an interim while waiting for the Invincibles, with Hermes, as well as Bulwark, also used as ASW helicopter carriers in the 70s.
The Bristols were not designed as DLGs, they grew from a missile-armed GP frigate concept, hence Type 82 following the Type 81 Tribal Class GP frigates (initial concepts for the Tribals included Tartar but this was dropped for cost reasons). The starting point was a Type 12 Leander hull form, optimised for sea keeping in the North Atlantic, but enlarged to fit the required systems, they were not an evolution of the Counties.
I need to dig out my dad's old photos from one of the SEATO exercises, he was on an RAN escort at the time. The carrier was Centaur; I can't recall which cruiser it was.
The RAN was never large enough to have a balanced fleet capable of generating more than one task group and then only some of the time. Post-war RN plans relied on the RAN providing (from memory) two escort groups and one amphibious group. This never eventuated, but I don't think the Australian government ever planned to do it, but considering the RN never achieved the force levels they required either, it is irrelevant for anything other than to show what they were thinking.
Realistically, the most the RAN would have been capable of sustaining in the 60s and into the 80s, was a small number of high-end platforms and maybe a dozen escorts. Malcom Fraser, when Defence Minister in the late 60s, stated the need for 23 destroyers and frigates and three carriers, which, of course, was never achieved.
The DDL program, for ten light destroyers, was part of this, as supplements for the existing six destroyers and six DEs (frigates).
With the failure of the various carrier replacement and supplementation programs of the 1960s, it was clear that a replacement CTOL carrier was never going to get up, making a helicopter carrier with the ability to operate Harriers as well as Sea Kings, the only option. The various refits and upgrades to Melbourne were only delaying the inevitable and led directly to Australia's loss of sea-based airpower.
A more realistic option would have been to accept this reality earlier and recast the RAN, again, as a cruiser and sloop fleet in the 1960s.
Instead of Melbourne upgrades, convert her (and Sydney) to helicopter carriers, and order Escort Cruisers instead of the three DDGs (or DLGs for that matter). They could be modified JdA or one of the UK designs; the Tartar versions were particularly interesting, with a through deck, Tartar, Seacat and a Mk 6 twin 4.5" mount, in addition to up to a dozen large ASW helicopters.
For each of these, have a GP destroyer and an ASW frigate. Spend the rest of the budget on modern day sloops.