I think he was great in the cinematic - the first one he had interaction with Saurfang and people learned that this guy that split earth open was on his very first battle had a positive impact, and that is trackable. He had his good moments, but he also had bad moments. And well he was meant to be a lil' bit childish because he was barely adolescent. But on the other hand, in some way Cinematics were weird, as Even a rookie Trolls should be much taller than Orcs. On each Chart possible Trolls are towering over orcs, but in cinematics it was the other way around. So How old he was? 14?
Anyway, I can see him growing to be someone great, but it needs to be handled carefully and he needs to drop that clucky and childish (I think you meant naive) aura about himself. There was a timeskip He is meant to be proper adult now, and he should act like one. But at the very same time I haveno faith that modern writers could do justice to trolls. They have very specific mindset and values and in DF besides Zandalari child, every other troll was failed, none of them talked like trolls, and I'm not talking about the accent.
I'm talking about things like that :
But I'm afraid he will be treated as pupil character forever. He needs to be thrown in some proper hardships to make him grow, and become a proper Darkpsear Champ.