Not sure if I'll be able to describe my issue but here goes.
Moved from AE7 to CS6 recently. I know, big jump.
In AE7 I had CC Light Rays applied to a text layer and had it make a left to right move behind some text and had a nice light ray effect that extended well beyond the text itself. In CS6 the light rays seem to be bounded by the size of the "text box"
You are correct - in CS6 and CC the CC Light Rays effect is limited to the box created by the text size. The workaround is to precomp the text and apply CC Light Rays to the precomp. I have no idea why that is - submit that as a bug to Adobe.