Unfortunately the gain is only incremental. The VT only makes AA a little more accurate - not anything remotely like one shot, one kill. Also, the RN destroyers are woefully undergunned for AA until 1945. Also without the remarkable fire control system of the American' 5"/38, its even harder to get hits.
So the capital ships of Force Z kill a few Nells and Bettys, but eventually a few get through. IOTL they survived a couple of attack runs, then Repulse (?) got 'anvilled' from two directions and it was downhill from there.
WW2 AA fire, even with the VT, wasn't a panacea. Part of the American success in the second half of the war was the layering of defenses (CAP, BARCAP, 5" guns, 40mm and 20mm). Attackers were attrited all the way into the target.