I might be wrong on this one, but let's see if I read EJ right.
After reading the whole weapon section of their enhancement post, there's this bit that stands out :
"In the end, Flame Tongue (enchant) allows the use of either a slow or a fast weapon with no major difference in DPS potential, as long as the fast weapon would be a significant upgrade in weapon DPS ans stats."
So this fast axe (the one in the OP) might actually be a good upgrade for most Enh Shaman but is not BiS.
Is this such a big problem?