After Effects - Blur doesn't feather

[MillyGallacher]

I have made a neon sign effect with text layers and the "wide glow" layer doesn't blur with a feathered edge. It will increase distance but always has a harsh solid edge which sort of ruins the lighting effect. 

I have tried every blur option in "blur & sharpen" and tried converting it to a shape layer to blur but that hasn't worked. 

Its hard to see on the black background but if you zoom in its very obvious - any help would be much appreciated!

[Mylenium]

Pre-compose the layer, apply the blur in the parent comp. A hacky workaround may be using the Grow Bounds effect, but it has a limite how far it can pad your rendering canvas for subsequent effects.

Mylenium