Did 'Son of Man' = בן איש?

The second century heretic Tatian explicitly said that Christianity forbade salvation to Adam.  It would seem very curious then if Tatian and his Encratite tradition would have understood Jesus's reference to messianic 'Son of Man' to be a ben Adam (בן אדם‎).  Instead we should look to the fact that Cain - a figure the heretics took a specific interest in not the least of which because of his being marked by a 'cross' - is identified as an ish - קָנִיתִי אִישׁ אֶת-יְהוָה (Gen 4:1).  There is also the fact to consider that while Adam is man in the lowest sense of the word, Ish represents the ideal concept of humanity. 

For those who aren't aware of it, the greatest authority in the Sephardic tradition in recent years wrote a book with this very title which is extremely influential in this community:

Yosef Chaim or in Iraqi Hebrew Yoseph Ḥayyim (1 September 1832 – 30 August 1909) (Hebrew: יוסף חיים מבגדאד) was a leading hakham (Sephardic Rabbi), authority on Jewish law (Halakha) and Master Kabbalist. He is best known as author of the work on Halakha Ben Ish Ḥai (בן איש חי) ("Son of Man (who) Lives"), a collection of the laws of everyday life interspersed with mystical insights and customs, addressed to the masses and arranged by the weekly Torah portion.