Tittle say it all, really.
Several threads have already confirmed, that tou can coin Heirlooms from Garrosh...
Fact (because I say so): TBC > Cata > Legion > ShaLa > MoP > DF > BfA > WoD = WotLK
My pet collection --> http://www.warcraftpets.com/collection/FuxieDK/