...You have a good point. I'd never really questioned how different Goron Link looked from Darmani, although he is missing a lot of features like his beard and the arm-length tattoos on his one arm. That and well, the big pointed hat. I'm surprised no one pointed that oddity out at all, now that I think about it. xD
Perhaps he looks just enough like Darmani to the Gorons to convince them? Even without the beard and extra tattoos, Goron Link is still wearing the same beads and gloves, and he actually does have those rockin' sideburns.
(Speaking of, I do recall that one Goron in the village does point out that your sideburns are what made him recognize you as Darmani! Guess that sort of hair-growing power is something not common in anyone but Goron heroes. *laugh*)