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Tanasijtshuk's 1986 paper is certainly the best resource out there, but when there is confusion, there are a couple of other papers (by Tanasijtshuk, or Raspi) that should be consulted. In other words, the 1986 work doesn't hold the magic final word! In any case, regarding you couple of specimens you mentioned:

"pair of black dots on the 2nd large tergite and a single dot on the fore margin of the two following tergites. It also has brown lines on thorax"
--whether this is Leucopis s.s., or Leucopomyia, this is the most typical situation, so this won't help for identification at all.

"unicolorous silvery abdomen and thorax but an interesting-looking arista. It is basally thickened and light yellow. Then there is a little darkened area and after that the arista is lighter again."
--the unicolorous silver abdomen and thorax is more uncommon, but the antennal character may help a little, but is not unique.

I would suggest that there are very few "spot characters" for any species of Leucopis, so I would not venture to suggest a name without seeing the specimen and dissecting the genitalia.