If you really have copied right ID in Light.dbc, it is quite possible that you have just entered wrong values for placement of light setting.:
pos.x = 17066.666 - pos.x / 36.0f;
pos.y = 17066.666 - pos.y / 36.0f;
pos.z = pos.z / 36.0f;
falloffStart = falloffStart / 36.0f;
falloffEnd = falloffEnd / 36.0f;
Those 36.0f mean 1 yard = 36 in value entered to DBC. It its also possible that you have entered wrong values for size of that light "ball". You see, there are two of them, inner and outer one. That outer one is always "less foggy", if you wish, and is interfering with surrounding lights. You may just need to expand both outer and especially inner ring's radius.