One of your points that does need addressing is the supposition that fleet AD can be handled by T45 (still some way off service entry). I remember similar comments on Sea Wolf and Sea Dart many years ago until it all went a bit pear-shaped down south.
There is no substitute for the ability to visually intercept and ID potential threats and deal with them if necessary, particularly when restrictive RoE are in force (USS Vincennes anyone?). The ability to counter LR surveillance and targetting aircraft also tends to be a bit handy - difficult if you have the "X" nm max range of A30. Finally, kill the archer not shoot his arrows remains a good maxim.
Some will say that E3 and other land-based assets might be able to provide this, but that logic didn't work in GIUK and there's no reason it should work now. That is why a good MASC solution and a half-decent AD capability in the CAG is still part of the requirement. It's not an "either/or" problem.