idk bro , I was in same dilemma couple of months before whether to send sponsor , employment, tax etc docS but I did prepared and sent just in case. Even I sent last 2 yrs tax and last 3,4 months bank account statement but my parents said consuler asked nothing about those doc. Just asked few questions like what u do, where do you work , how many children etc .I think sponser letter alone should be enough just in case otherwise you don't need other docs.