The background story of Valungu needs some tweaking(I didn't feel a connection between him leaving his village, of which he is likely very loyal to- to aid the Horde. Tad 'off' putting to the viewer.) in order to make a forest troll work with the setting. I like the idea, as in Thrall's new horde, there was established positive-resulting contact between Thrall's horde and the Revantusk tribe so there's clear purpose in doing so, just justify it more clearly as to why he leaves his precious home for unfamiliar lands.
That said, as Sevencix stated- no working models are as of yet enabled(Crossing fingers for future troll hype).
*update* We have at least one forest troll model coming next patch, which can wear all available clothing.