This plan has gone by the board, and as a result, there are now just three AD units - two Typhoon squadrons and a single, under-strength F3 unit. Is the latter needed? Yes, it is. And then some. Two Typhoon units are insufficient to maintain Southern QRA, the Falklands commitment, and to maintain currency in the A-G role, let alone taking over Northern QRA as well.
QRA against who? The only credible airborne threat against the UK currently is from terrorist pilots. The QRA Typhoons are no deterrent or defence against them. All a terrorist would need to do is file a flight plan to overfly London to one of the satellite airfields and in the time taken to divert from the flight plan and hit the target, the QRA Typhoons would not even be at the end of their take-off run.
If Russia wanted to attack us (why on earth would they want to?) they are probably not even capable of launching a conventional sustainable aerial attack against us. Even if they did establish air superiority, what could they do next? They don't have anything like enough airborne or amphibious troops to actually invade and hold the ground, nor enough assets to enforce a trade blockade. RAF air defence thinking is still mired in WW2 mindset.
As for Argentina attacking the Malvinas - in '82 they had a military junta that was not accountable to the population and which had the tacit support of a superpower (USA) - they are now a democracy with international obligations and responsibility to their electorate. There would not be public support for an invasion, and Argentina would become a pariah nation.
The A-G role for the Typhoon? Maybe in the distant future, if it gets deployed to Afghanistan, then maybe the RAF should start to build that capability. But there are currently far, far higher priorities - especially ground troops who are currently training for deployment to Herrick XIV. I will be going (as a TA Officer) and we don't even get enough ammunition to carry out realistic live-firing training. So why are we wasting money maintaining Typhoon A-G capability when there are no current plans to use it?
As you guessed, my "other job" is in aviation - as pilot and TRI on a bizjet.