I have consistently defended Johnstone, I think he has shown signs of improvement, how much of that is because of improved defensive performance is hard to say, Foster played behind a solid defence even when we got relegated, with the signing of Holgate and the removal of Bartley the defence is suddenly much improved.
Johnstone is very rarely at fault for goals and regularly makes superb saves, he is not the complete keeper but neither is he the liability some have suggested, overall, he is doing quite well I think.